64 results on '"Zong-Wen Yu"'
Search Results
2. Sending-or-not-sending twin field quantum key distribution with imperfect vacuum sources
- Author
-
Xiao-Long Hu, Cong Jiang, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
quantum key distribution ,sending-or-not-sending protocol ,decoy state method ,imperfect vacuum source ,Science ,Physics ,QC1-999 - Abstract
The sending-or-not-sending (SNS) protocol of the twin-field (TF) quantum key distribution (QKD) can tolerant large misalignment error and its key rate can exceed the linear bound of repeaterless QKD. The original SNS protocol and all variants of TF-QKD require perfect vacuum sources, but in the real world experiments there is no practical perfect vacuum source. Instead, experimenters use extremely weak sources to substitute vacuum sources, which may break the security of the protocol. Here we propose an SNS protocol with imperfect vacuum sources and give the non-asymptotic decoy-state analysis of this protocol. Our numerical simulation shows that when the imperfect vacuum sources are close to perfect vacuum sources, our protocol can obtain similar key rate as that with perfect vacuum sources. This is the first result that closes the potential security loophole due to imperfect vacuum of TF-QKD.
- Published
- 2022
- Full Text
- View/download PDF
3. Composable security for practical quantum key distribution with two way classical communication
- Author
-
Cong Jiang, Xiao-Long Hu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
TWCC ,composable security ,SNS ,quantum key distribution ,QKD ,Science ,Physics ,QC1-999 - Abstract
We present a theory for the composable security of sending-or-not-sending (SNS) protocol of twin field quantum key distribution (TF-QKD). We present methods to strictly calculate the finite-key effects in QKD with error rejection through two-way classical communication (TWCC) for SNS TF-QKD protocol. Unlike the normal QKD without TWCC, here the probability of tagging or untagging for each two-bit random group is not independent. We rigorously solve this problem by imagining a virtual set of bits where every bit is independent and identical. With explicit formulas, we show that simply applying Chernoff bound in the calculation gives correct key rate, but the failure probability changes a little bit. We calculate the key rate with strict bounds and security, and obtain key rates by far breaking the PLOB (Pirandola, Laurenza, Ottaviani, and Banchi) bound with composable security.
- Published
- 2021
- Full Text
- View/download PDF
4. Sending-or-not-sending twin-field quantum key distribution with discrete-phase-randomized weak coherent states
- Author
-
Cong Jiang, Zong-Wen Yu, Xiao-Long Hu, and Xiang-Bin Wang
- Subjects
Physics ,QC1-999 - Abstract
In many security proofs of quantum key distribution, the random phases of coherent states are assumed to be continuously modulated. However, in practice, we can only take discrete phase randomization to coherent-state sources. In this paper, we study the sending-or-not-sending (SNS) protocol with discrete-phase-randomized coherent states. We present the security proof of the SNS protocol with discrete phase modulation. We then present analytic formulas for key rate calculation. With the decoy-state method and the properties of trace distance, we get the analytical formula of the upper bound of the phase-flip error rate. We also get the lower bound of the yield of untagged bits, which can be calculated by either analytical formula or linear programming. Our numerical simulation results show that with only six phase values, the key rates of the SNS protocol can exceed the linear bound and, with 12 phase values, the key rates are very close to the results of the SNS protocol with continuously modulated phase randomization.
- Published
- 2020
- Full Text
- View/download PDF
5. Zigzag approach to higher key rate of sending-or-not-sending twin field quantum key distribution with finite-key effects
- Author
-
Cong Jiang, Xiao-Long Hu, Hai Xu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
SNS-TF QKD ,finite key effects ,odd parity error rejection ,Science ,Physics ,QC1-999 - Abstract
Odd-parity error rejection (OPER), in particular the method of actively odd parity pairing (AOPP), can drastically improve the asymptotic key rate of sending-or-not-sending twin-field (SNS-TF) quantum key distribution (QKD). However, in practice, the finite-key effects have to be considered for the security. Here, we propose a zigzag approach to verify the phase-flip error of the survived bits after OPER or AOPP. Based on this, we can take all the finite-key effects efficiently in calculating the non-asymptotic key rate. Numerical simulation shows that our approach here produces the highest key rate over all distances among all existing methods, improving the key rate by more than 100% to 3000% in comparison with different prior art methods with typical experimental setting. These verify the advantages of the AOPP method with finite data size. Also, with our zigzag approach here, the non-asymptotic key rate of SNS-TF QKD can by far break the absolute bound of repeater-less key rate with whatever detection efficiency. We can even reach a non-asymptotic key rate more than 40 times of the practical bound and 13 times of the absolute bound with 10 ^12 pulses.
- Published
- 2020
- Full Text
- View/download PDF
6. Round robin differential phase shift quantum key distribution with yes-no detectors only
- Author
-
Cong, Jiang, Zong-Wen, Yu, and Xiang-Bin, Wang
- Subjects
Quantum Physics - Abstract
In the original round-robin differential-phase-shift (RRDPS) quantum key distribution and its improved method, the photon-number-resolving detectors are must for the security. We present a RRDPS protocol with yes-no detectors only. We get the upper bounds of mutual information of Alice and Eve, and Bob and Eve, and the formula of key rate. Our main idea is to divide all counts into two classes, the counts due to the odd number photons of incident detectors and the counts due to the even number photons of incident detectors. The fact that the bit-flip error rate of the later class is certainly $50\%$ makes it possible for us to perform a tightened estimation of the upper bound of the leakage information. The robustness of original RRDPS against source flaws such as side-channel attacks still holds for the RRDPS with yes-no detectors. The simulation results show that the key rate of RRDPS with yes-no detectors is close to that of RRDPS with photon-number-resolving detectors. Our results make the RRDPS protocol much more practical.
- Published
- 2019
7. Experimental Twin-Field Quantum Key Distribution Through Sending-or-Not-Sending.
- Author
-
Yang Liu, Zong-Wen Yu, Weijun Zhang, Jian-Yu Guan, Jiu-Peng Chen, Chi Zhang, Xiaolong Hu, Hao Li, Teng-Yun Chen, Lixing You, Zhen Wang, Xiang-Bin Wang, Qiang Zhang, and Jian-Wei Pan
- Published
- 2019
8. Robust twin-field quantum key distribution through sending or not sending
- Author
-
Cong Jiang, Zong-Wen Yu, Xiao-Long Hu, and Xiang-Bin Wang
- Subjects
Quantum Physics ,Multidisciplinary ,FOS: Physical sciences ,Quantum Physics (quant-ph) - Abstract
The sending-or-not-sending (SNS) protocol is one of the most major variants of the twin-field (TF) quantum key distribution (QKD) protocol and has been realized in a 511-km field fiber, the farthest field experiment to date. In practice, however, all decoy-state methods have unavoidable source errors, and the source errors may be non-random, which compromises the security condition of the existing TF-QKD protocols. In this study, we present a general approach for efficiently calculating the SNS protocol’s secure key rate with source errors, by establishing the equivalent protocols through virtual attenuation and the tagged model. This makes the first result for TF QKD in practice where source intensity cannot be controlled exactly. Our method can be combined with the two-way classical communication method such as active odd-parity pairing to further improve the key rate. The numerical results show that if the intensity error is within a few percent, the key rate and secure distance only decrease marginally. The key rate of the recent SNS experiment in the 511-km field fiber is still positive using our method presented here, even if there is a $\pm 9.5\%$ intensity fluctuation. This shows that the SNS protocol is robust against source errors.
- Published
- 2022
9. Experimental Side-Channel-Secure Quantum Key Distribution
- Author
-
Chi Zhang, Xiao-Long Hu, Cong Jiang, Jiu-Peng Chen, Yang Liu, Weijun Zhang, Zong-Wen Yu, Hao Li, Lixing You, Zhen Wang, Xiang-Bin Wang, Qiang Zhang, and Jian-Wei Pan
- Subjects
Quantum Physics ,FOS: Physical sciences ,General Physics and Astronomy ,Quantum Physics (quant-ph) ,Computer Science::Cryptography and Security - Abstract
Quantum key distribution can provide unconditionally secure key exchange for remote users in theory. In practice, however, in most quantum key distribution systems, quantum hackers might steal the secure keys by listening to the side channels in the source, such as the photon frequency spectrum, emission time, propagation direction, spatial angular momentum, and so on. It is hard to prevent such kinds of attacks because side channels may exist in any of the encoding space whether the designers take care of or not. Here we report an experimental realization of a side-channel-free quantum key distribution protocol which is not only measurement-device-independent, but also immune to all side-channel attacks in the source. We achieve a secure key rate of 4.80e-7 per pulse through 50 km fiber spools., Comment: 23 pages, 5 figures
- Published
- 2022
10. Sending-or-Not-Sending Twin-Field Quantum Key Distribution with Redundant Space
- Author
-
Hai Xu, Xiao-Long Hu, Cong Jiang, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Quantum Physics ,General Physics and Astronomy ,FOS: Physical sciences ,Quantum Physics (quant-ph) - Abstract
We propose to adopt redundant space such as polarization mode in the sending-or-not-sending Twin-Field quantum key distribution (TF-QKD) in the Fock space. With the help of redundant space such as photon polarization, we can post-select events according to the outcome of the observation to the additional quantity. This compresses the bit-flip error rate in the post-selected events of the SNS protocol. The calculation shows that the method using redundant space can greatly improve the performance in practical TF-QKD, especially when the total number of pulses is small., This manuscript has been accepted for publication as a Regular Article in Physical Review Research
- Published
- 2022
11. Guessing probability in quantum key distribution
- Author
-
Zong-Wen Yu, Xiang-Bin Wang, Cong Jiang, Jing-Tao Wang, and Ji-Qian Qin
- Subjects
Computer Networks and Communications ,FOS: Physical sciences ,02 engineering and technology ,Quantum key distribution ,01 natural sciences ,Upper and lower bounds ,Prime (order theory) ,lcsh:QA75.5-76.95 ,Orders of magnitude (bit rate) ,Simple (abstract algebra) ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Computer Science (miscellaneous) ,Trace distance ,010306 general physics ,Mathematics ,Discrete mathematics ,Quantum Physics ,Basis (linear algebra) ,020206 networking & telecommunications ,Statistical and Nonlinear Physics ,lcsh:QC1-999 ,Computational Theory and Mathematics ,Bounded function ,lcsh:Electronic computers. Computer science ,Quantum Physics (quant-ph) ,lcsh:Physics - Abstract
On the basis of the existing trace distance result, we present a simple and efficient method to tighten the upper bound of the guessing probability. The guessing probability of the final key k can be upper bounded by the guessing probability of another key k', if k' can be mapped from the final key k. Compared with the known methods, our result is more tightened by thousands of orders of magnitude. For example, given a 10^{-9}-secure key from the sifted key, the upper bound of the guessing probability obtained using our method is 2*10^(-3277). This value is smaller than the existing result 10^(-9) by more than 3000 orders of magnitude. Our result shows that from the perspective of guessing probability, the performance of the existing trace distance security is actually much better than what was assumed in the past., published version (with typing error corrected)
- Published
- 2020
12. Universal approach to sending-or-not-sending twin field quantum key distribution
- Author
-
Xiao-Long Hu, Cong Jiang, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Quantum Physics ,Physics and Astronomy (miscellaneous) ,Materials Science (miscellaneous) ,FOS: Physical sciences ,Electrical and Electronic Engineering ,Quantum Physics (quant-ph) ,Atomic and Molecular Physics, and Optics - Abstract
We present a universal approach to sending-or-not-sending (SNS) protocol of twin-field quantum key distribution with the method of actively odd parity pairing. In this improved protocol, the code bits are not limited to heralded events in time windows participated by pulses of intensity μ z and vacuum. All kinds of heralded events can be used for code bits to distill the final keys. The number of intensities (3 or 4) and the kinds of heralded events for code bits are automatically chosen by the key rate optimization itself. Numerical simulation shows that the key rate rises drastically in typical settings, up to 80% improvement compared with the prior results. Also, larger intensity value can be used for decoy pulses. This makes the protocol more robust in practical experiments.
- Published
- 2022
13. Measurement-device-independent quantum key distribution protocol with phase post-selection
- Author
-
Cong Jiang, Xiao-Long Hu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Abstract
Measurement-device-independent quantum key distribution (MDI-QKD) protocol can remove all the loopholes of the detection devices and, thus, has attracted much attention. Based on the technique of single-photon interference, we propose a modified MDI-QKD protocol with phase post-selection. We prove the security of the announcement of the private phases in the X basis and show how to apply the phase post-selection method to the double-scanning four-intensity MDI-QKD protocol. The numerical results show that the phase post-selection method can significantly improve the key rates at all distances. In the double-scanning method, two parameters need to be scanned in the calculation of the final key rate, and the global parameter optimization is pretty time-consuming. We propose an accelerated method that can greatly reduce the running time of the global parameter optimization program. This makes the method practically useful in an unstable channel.
- Published
- 2022
14. Field Test of Twin-Field Quantum Key Distribution through Sending-or-Not-Sending over 428 km
- Author
-
Wei-Jun Zhang, Hao Li, Xiang-Bin Wang, Teng-Yun Chen, Lixing You, Hai Xu, Hao-Tao Zhu, Fei Zhou, Zhi-Yong Han, Mi Zou, Hui Liu, J. Chen, Zhang Hongbo, Hua Yong, Jian-Wei Pan, Xiaolong Hu, Cong Jiang, Shi-Zhao Ma, Zhen Wang, Zong-Wen Yu, Hongkun Hu, Shi-Biao Tang, Dai Yunqi, and Qiang Zhang
- Subjects
Quantum Physics ,Computer science ,Fiber (mathematics) ,business.industry ,Measure (physics) ,Electrical engineering ,General Physics and Astronomy ,FOS: Physical sciences ,Quantum key distribution ,Stability (probability) ,Field (computer science) ,Pairing ,Key (cryptography) ,business ,Quantum Physics (quant-ph) ,Parity bit - Abstract
Quantum key distribution endows people with information-theoretical security in communications. Twin-field quantum key distribution (TF-QKD) has attracted considerable attention because of its outstanding key rates over long distances. Recently, several demonstrations of TF-QKD have been realized. Nevertheless, those experiments are implemented in the laboratory, and therefore a critical question remains about whether the TF-QKD is feasible in real-world circumstances. Here, by adopting the sending-or-not-sending twin-field QKD (SNS-TF-QKD) with the method of actively odd parity pairing (AOPP), we demonstrate a field-test QKD over 428 km of deployed commercial fiber and two users are physically separated by about 300 km in a straight line. To this end, we explicitly measure the relevant properties of the deployed fiber and develop a carefully designed system with high stability. The secure key rate we achieved breaks the absolute key rate limit of repeaterless QKD. The result provides a new distance record for the field test of both TF-QKD and all types of fiber-based QKD systems. Our work bridges the gap of QKD between laboratory demonstrations and practical applications and paves the way for an intercity QKD network with measurement-device-independent security.
- Published
- 2021
- Full Text
- View/download PDF
15. Sending-or-not-sending twin-field quantum key distribution with discrete-phase-randomized weak coherent states
- Author
-
Xiaolong Hu, Zong-Wen Yu, Cong Jiang, and Xiang-Bin Wang
- Subjects
Physics ,Hardware_MEMORYSTRUCTURES ,Field (physics) ,Quantum mechanics ,Phase (waves) ,Coherent states ,Quantum key distribution ,Protocol (object-oriented programming) - Abstract
The authors show the effect of the sending-or-not-sending twin-field protocol with only a few values of discrete phases for the weak coherent states.
- Published
- 2020
16. Sending-or-not-sending twin-field quantum key distribution: Breaking the direct transmission key rate
- Author
-
Xiang-Bin Wang, Xiaolong Hu, Zong-Wen Yu, Hai Xu, and Cong Jiang
- Subjects
Physics ,Protocol (science) ,Field (physics) ,Word error rate ,Quantum key distribution ,Absolute limit ,01 natural sciences ,010305 fluids & plasmas ,Transmission (telecommunications) ,Pairing ,0103 physical sciences ,Key (cryptography) ,010306 general physics ,Algorithm - Abstract
We present improved results of sending-or-not-sending twin-field quantum key distribution by using error rejection through two-way classical communications. Our error rejection method, especially our method of actively odd-parity pairing (AOPP) can drastically improve the performance of sending-or-not-sending twin-field protocol in both secure distance and key rate. Taking a typical experimental parameter setting, our method here improves the secure distance by 70 km to more than 100 km in comparison with the prior art results. Comparative study also shows advantageous in key rates at regime of long distance and large misalignment error rate for our method here. The numerical results show that our method here can significantly exceed the absolute limit of direct transmission key rate, and also have an advantageous key rates higher than various prior art results by 10 to 20 times.
- Published
- 2020
17. Higher key rate of measurement-device-independent quantum key distribution through joint data processing
- Author
-
Cong Jiang, Xiang-Bin Wang, Zong-Wen Yu, and Xiaolong Hu
- Subjects
Protocol (science) ,Physics ,Quantum Physics ,Work (thermodynamics) ,Data processing ,Key (cryptography) ,Word error rate ,FOS: Physical sciences ,Quantum key distribution ,Joint (audio engineering) ,Quantum Physics (quant-ph) ,Algorithm ,Communication channel - Abstract
We propose a method named as double-scanning method, to improve the key rate of measurement-device-independent quantum key distribution (MDI-QKD) drastically. In the method, two parameters are scanned simultaneously to tightly estimate the counts of single-photon pairs and the phase-flip error rate jointly. Numerical results show that the method in this work can improve the key rate by $35\%-280\%$ in a typical experimental set-up. Besides, we study the optimization of MDI-QKD protocol with all parameters including the source parameters and failure probability parameters, over symmetric channel or asymmetric channel. Compared with the optimized results with only the source parameters, the all-parameter-optimization method could improve the key rate by about $10\%$.
- Published
- 2020
- Full Text
- View/download PDF
18. Sending-or-not-sending twin-field protocol for quantum key distribution with asymmetric source parameters
- Author
-
Xiaolong Hu, Cong Jiang, Xiang-Bin Wang, and Zong-Wen Yu
- Subjects
Physics ,Quantum Physics ,business.industry ,FOS: Physical sciences ,Quantum key distribution ,01 natural sciences ,Field (computer science) ,010305 fluids & plasmas ,Condensed Matter::Superconductivity ,0103 physical sciences ,Computer Science::Networking and Internet Architecture ,Key (cryptography) ,ComputingMilieux_COMPUTERSANDSOCIETY ,Physics::Accelerator Physics ,Quantum Physics (quant-ph) ,010306 general physics ,business ,Protocol (object-oriented programming) ,Computer Science::Cryptography and Security ,Communication channel ,Computer network - Abstract
The sending-or-not-sending (SNS) protocol of the twin-field quantum key distribution (TFQKD) can tolerant large misalignment error and its key rate can exceed the bound of repeaterless QKD. But the original SNS protocol requires the two users to use the same source parameters. Here we propose a general protocol with asymmetric source parameters and give the security proof of this protocol. Our general protocol has a much better performance than that of the original SNS protocol when the channel of the system is asymmetric., submitted to PRA on Aug. 12
- Published
- 2019
19. Practical Long-Distance Side-Channel-Free Quantum Key Distribution
- Author
-
Xiaolong Hu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Secure communication ,business.industry ,Computer science ,General Physics and Astronomy ,Word error rate ,Mature technology ,Side channel attack ,State (computer science) ,Quantum key distribution ,business ,Communication channel ,Computer network - Abstract
Quantum key distribution (QKD) can provide secure communication even when an eavesdropper (the villainous ``Eve'') completely controls the channel. In practice, though, side-channel effects exist due to device imperfections, and Eve can still intercept information via a side channel. Thus the authors devise a QKD scheme that is both free of side channels in the source state and measurement-device-independent. While some other protocols can also achieve side-channel-free security, this one is based on mature technology without any demand for local detection efficiency, and works for distances greater than 200 km, even though the misalignment error rate may be as large as 20%.
- Published
- 2019
20. Sending-or-Not-Sending with Independent Lasers: Secure Twin-Field Quantum Key Distribution Over 509 km
- Author
-
Jian-Wei Pan, Hao Chen, Zhen Wang, Jian-Yu Guan, Zong-Wen Yu, Jin Lin, Cong Jiang, Yang Liu, Lixing You, Weijun Zhang, Xiaolong Hu, Hao Li, Ming-Jun Li, J. Chen, Hai Xu, Chi Zhang, Qiang Zhang, and Xiang-Bin Wang
- Subjects
Infinite number ,Quantum Physics ,Optical fiber ,Computer science ,General Physics and Astronomy ,Key distribution ,FOS: Physical sciences ,Quantum key distribution ,Laser ,01 natural sciences ,law.invention ,Optical path ,law ,0103 physical sciences ,Electronic engineering ,010306 general physics ,Quantum Physics (quant-ph) - Abstract
Twin field quantum key distribution promises high key rates at long distance to beat the rate distance limit. Here, applying the sending or not sending TF QKD protocol, we experimentally demonstrate a secure key distribution breaking the absolute key rate limit of repeaterless QKD over 509 km, 408 km ultra-low loss optical fibre and 350 km standard optical fibre. Two independent lasers are used as the source with remote frequency locking technique over 500 km fiber distance; Practical optical fibers are used as the optical path with appropriate noise filtering; And finite key effects are considered in the key rate analysis. The secure key rates obtained at different distances are more than 5 times higher than the conditional limit of repeaterless QKD, a bound value assuming the same detection loss in the comparison. The achieved secure key rate is also higher than that a traditional QKD protocol running with a perfect repeaterless QKD device and even if an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve high secure key rate at long distribution distance, and hence practically useful for field implementation of intercity QKD., 17 pages, 10 figures and 8 tables
- Published
- 2019
21. Experimental 4-intensity decoy-state quantum key distribution with asymmetric basis-detector efficiency
- Author
-
Hui Liu, Jian-Wei Pan, Mi Zou, Teng-Yun Chen, Yan-Lin Tang, Xiang-Bin Wang, Yong Zhao, Jun Zhang, and Zong-Wen Yu
- Subjects
Protocol (science) ,Physics ,Quantum Physics ,Work (thermodynamics) ,Decoy state ,Basis (linear algebra) ,media_common.quotation_subject ,Detector ,FOS: Physical sciences ,Quantum key distribution ,Topology ,01 natural sciences ,Asymmetry ,010305 fluids & plasmas ,0103 physical sciences ,Key (cryptography) ,Quantum Physics (quant-ph) ,010306 general physics ,media_common - Abstract
The decoy-state method has been developed rapidly in quantum key distribution (QKD) since it is immune to photon-number splitting attacks. However, two basis detector efficiency asymmetry, which exists in realistic scenarios, has been ignored in the prior results. By using the recent 4-intensity decoy-state optimization protocol, we report the first implementation of high-rate QKD with asymmetric basis detector efficiency, demonstrating 1.9 to 33.2 times higher key rate than previous protocols in the situation of large basis detector efficiency asymmetry. The results ruled out an implicitly assumption in QKD that the efficiency of Z basis and X basis are restricted to be same. This work paves the way towards a more practical QKD setting.
- Published
- 2019
22. Practical Long‐Distance Measurement‐Device‐Independent Quantum Key Distribution By Four‐Intensity Protocol
- Author
-
Cong Jiang, Xiao-Long Hu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Physics ,Nuclear and High Energy Physics ,Decoy state ,Statistical and Nonlinear Physics ,Quantum key distribution ,Condensed Matter Physics ,Topology ,Electronic, Optical and Magnetic Materials ,Intensity (physics) ,Distance measurement ,Computational Theory and Mathematics ,Electrical and Electronic Engineering ,Protocol (object-oriented programming) ,Mathematical Physics - Published
- 2021
23. Experimental Twin-Field Quantum Key Distribution through Sending or Not Sending
- Author
-
Zhen Wang, Xiaolong Hu, Zong-Wen Yu, Xiang-Bin Wang, Qiang Zhang, Jin Lin, Cong Jiang, Yang Liu, Lixing You, Jian-Wei Pan, Teng-Yun Chen, Chi Zhang, J. Chen, Hao Li, Jian-Yu Guan, and Weijun Zhang
- Subjects
FOS: Computer and information sciences ,Physics ,Quantum Physics ,Computer Science - Cryptography and Security ,Photon ,Optical fiber ,Phase (waves) ,FOS: Physical sciences ,General Physics and Astronomy ,Quantum key distribution ,Interference (wave propagation) ,01 natural sciences ,law.invention ,law ,0103 physical sciences ,Key (cryptography) ,Electronic engineering ,Linear scale ,Quantum Physics (quant-ph) ,010306 general physics ,Cryptography and Security (cs.CR) ,Communication channel - Abstract
Channel loss seems to be the most severe limitation on the practical application of long distance quantum key distribution. The idea of twin-field quantum key distribution can improve the key rate from the linear scale of channel loss in the traditional decoy-state method to the square root scale of the channel transmittance. However, the technical demanding is rather tough because it requests single photon level interference of two remote independent lasers. Here, we adopt the technology developed in the frequency and time transfer to lock two independent lasers' wavelengths and utilize additional phase reference light to estimate and compensate the fiber fluctuation. Further with a single photon detector with high detection rate, we demonstrate twin field quantum key distribution through the sending-or-not-sending protocol with realistic phase drift over 300 km optical fiber spools. We calculate the secure key rates with finite size effect. The secure key rate at 300 km ($1.96\times10^{-6}$) is higher than that of the repeaterless secret key capacity ($8.64\times10^{-7}$)., 34 pages, 10 figures and 9 tables
- Published
- 2019
24. Zigzag approach to higher key rate of sending-or-not-sending twin field quantum key distribution with finite key effects
- Author
-
Xiang-Bin Wang, Zong-Wen Yu, Xiao-Long Hu, Hai Xu, and Cong Jiang
- Subjects
Physics ,Quantum Physics ,Computer simulation ,General Physics and Astronomy ,FOS: Physical sciences ,Field (mathematics) ,Quantum key distribution ,01 natural sciences ,010305 fluids & plasmas ,Zigzag ,Pairing ,0103 physical sciences ,Key (cryptography) ,010306 general physics ,Quantum Physics (quant-ph) ,Algorithm ,Parity bit - Abstract
Odd-parity error rejection (OPER), in particular the method of actively odd parity pairing (AOPP), can drastically improve the asymptotic key rate of sending-or-not-sending twin-field (SNS-TF) quantum key distribution (QKD). However, in practice, the finite-key effects have to be considered for the security. Here, we propose a zigzag approach to verify the phase-flip error of the survived bits after OPER or AOPP. Based on this, we can take all the finite-key effects efficiently in calculating the non-asymptotic key rate. Numerical simulation shows that our approach here produces the highest key rate over all distances among all existing methods, improving the key rate by more than 100% to 3000% in comparison with different prior art methods with typical experimental setting. These verify the advantages of the AOPP method with finite data size. Also, with our zigzag approach here, the non-asymptotic key rate of SNS-TF QKD can by far break the absolute bound of repeater-less key rate with whatever detection efficiency. We can even reach a non-asymptotic key rate more than 40 times of the practical bound and 13 times of the absolute bound with 1012 pulses.
- Published
- 2019
25. Sending-or-not-sending twin-field quantum key distribution in practice
- Author
-
Xiang-Bin Wang, Zong-Wen Yu, Hai Xu, Xiaolong Hu, and Cong Jiang
- Subjects
0301 basic medicine ,Infinite number ,Multidisciplinary ,Computer simulation ,Field (physics) ,lcsh:R ,Phase (waves) ,lcsh:Medicine ,Statistical fluctuations ,Quantum key distribution ,Article ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,lcsh:Q ,Statistical physics ,lcsh:Science ,030217 neurology & neurosurgery ,Key size ,Mathematics - Abstract
Recently, the twin field quantum key distribution (TF-QKD) protocols have been investigated extensively. In particular, an efficient protocol for TF-QKD with sending or not sending the coherent state has been given in. Here in this paper, we present results of practical sending-or-not-sending (SNS) twin field quantum key distribution. In real-life implementations, we need consider the following three requirements, a few different intensities rather than infinite number of different intensities, a phase slice of appropriate size rather than infinitely small size and the statistical fluctuations. We first show the decoy-state method with only a few different intensities and a phase slice of appropriate size. We then give a statistical fluctuation analysis for the decoy-state method. Numerical simulation shows that, the performance of our method is comparable to the asymptotic case for which the key size is large enough. Our method can beat the PLOB bound on secret key capacity. Our results show that practical implementations of the SNS quantum key distribution can be both secure and efficient.
- Published
- 2019
26. Unconditional security of sending or not sending twin-field quantum key distribution with finite pulses
- Author
-
Cong Jiang, Xiao-Long Hu, Xiang-Bin Wang, and Zong-Wen Yu
- Subjects
Quantum Physics ,Computer simulation ,business.industry ,Computer science ,General Physics and Astronomy ,FOS: Physical sciences ,Fault tolerance ,02 engineering and technology ,Quantum key distribution ,021001 nanoscience & nanotechnology ,Encryption ,Topology ,01 natural sciences ,Field (computer science) ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,business ,Quantum Physics (quant-ph) ,Protocol (object-oriented programming) ,Finite set ,Key size ,Computer Science::Cryptography and Security - Abstract
The Sending-or-Not-Sending protocol of the twin-field quantum key distribution (TF-QKD) has its advantage of unconditional security proof under any coherent attack and fault tolerance to large misalignment error. So far this is the only coherent-state based TF-QKD protocol that has considered finite-key effect, the statistical fluctuations. Here we consider the complete finite-key effects for the protocol and we show by numerical simulation that the protocol with typical finite number of pulses in practice can produce unconditional secure final key under general attack, including all coherent attacks. It can exceed the secure distance of 500 $km$ in typical finite number of pulses in practice even with a large misalignment error., Comment: Our results with finite number of pulses are secure under general attacks including whatever coherent attack
- Published
- 2019
- Full Text
- View/download PDF
27. Twin-field quantum key distribution with large misalignment error
- Author
-
Xiang-Bin Wang, Xiaolong Hu, and Zong-Wen Yu
- Subjects
Physics ,Word error rate ,Eavesdropping ,Quantum key distribution ,Interference (wave propagation) ,01 natural sciences ,010305 fluids & plasmas ,Postselection ,0103 physical sciences ,Key (cryptography) ,010306 general physics ,Quantum information science ,Algorithm ,Communication channel - Abstract
Based on the novel idea of twin-field quantum key distribution [TF-QKD; Lucamarini et al., Nature (London) 557, 400 (2018)], we present a protocol named the ``sending or not sending TF-QKD'' protocol, which can tolerate large misalignment error. A revolutionary theoretical breakthrough in quantum communication, TF-QKD changes the channel-loss dependence of the key rate from linear to square root of channel transmittance. However, it demands the challenging technology of long-distance single-photon interference, and also, as stated in the original paper, the security proof was not finalized there due to the possible effects of the later announced phase information. Here we show by a concrete eavesdropping scheme that the later phase announcement does have important effects and the traditional formulas of the decoy-state method do not apply to the original protocol. We then present our ``sending or not sending'' protocol. Our protocol does not take postselection for the bits in $Z$-basis (signal pulses), and hence the traditional decoy-state method directly applies and automatically resolves the issue of security proof. Most importantly, our protocol presents a negligibly small error rate in $Z$-basis because it does not request any single-photon interference in this basis. Thus our protocol greatly improves the tolerable threshold of misalignment error in single-photon interference from the original a few percent to more than $45%$. As shown numerically, our protocol exceeds a secure distance of 700, 600, 500, or 300 km even though the single-photon interference misalignment error rate is as large as $15%, 25%, 35%$, or $45%$.
- Published
- 2018
28. Measurement-Device-Independent Quantum Key Distribution over asymmetric channel and unstable channel
- Author
-
Yuan Cao, Xiang-Bin Wang, Zong-Wen Yu, and Xiaolong Hu
- Subjects
Physics ,Multidisciplinary ,Computer simulation ,lcsh:R ,lcsh:Medicine ,Quantum channel ,Quantum key distribution ,Statistical fluctuations ,Topology ,01 natural sciences ,Article ,010305 fluids & plasmas ,Joint constraints ,0103 physical sciences ,Key (cryptography) ,lcsh:Q ,lcsh:Science ,010306 general physics ,Global optimization ,Communication channel - Abstract
We show that a high key rate of Measurement-Device-Independent Quantum Key Distribution (MDIQKD) over asymmetric and unstable quantum channel can be obtained by full optimization and compensation. Employing a gradient optimization method, we make the full optimization taking both the global optimization for the 12 independent parameters and the joint constraints for statistical fluctuations. We present a loss-compensation method by monitoring the channel loss for an unstable channel. The numerical simulation shows that the method can produce high key rate for both the asymmetric channel and the unstable channel. Compared with the existing results of independent constraints, our result here improves the key rate by 1 to tens of times in typical experimental conditions.
- Published
- 2018
29. Efficient measurement-device-independent quantum key distribution without vacuum sources
- Author
-
Xiao-Long Hu, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
0103 physical sciences ,010306 general physics ,01 natural sciences ,010305 fluids & plasmas - Published
- 2018
30. Measurement-device-independent quantum key distribution with correlated source-light-intensity errors
- Author
-
Cong Jiang, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Physics ,Imagination ,Attenuation ,media_common.quotation_subject ,Quantum key distribution ,01 natural sciences ,Intensity (physics) ,Computational physics ,010309 optics ,Light intensity ,Measurement device ,0103 physical sciences ,Key (cryptography) ,010306 general physics ,media_common ,Communication channel - Abstract
We present an analysis for measurement-device-independent quantum key distribution with correlated source-light-intensity errors. Numerical results show that the results here can greatly improve the key rate especially with large intensity fluctuations and channel attenuation compared with prior results if the intensity fluctuations of different sources are correlated.
- Published
- 2018
31. Measurement-device-independent quantum key distribution via quantum blockade
- Author
-
Ao Li, Xiang-Bin Wang, Cong Jiang, Xiaolong Hu, Yi-Heng Zhou, and Zong-Wen Yu
- Subjects
Protocol (science) ,Multidisciplinary ,Computer simulation ,Computer science ,lcsh:R ,lcsh:Medicine ,Quantum key distribution ,Topology ,01 natural sciences ,Article ,010305 fluids & plasmas ,Blockade ,Measurement device ,0103 physical sciences ,Key (cryptography) ,Coherent states ,lcsh:Q ,lcsh:Science ,010306 general physics ,Quantum ,Computer Science::Cryptography and Security - Abstract
Efficiency in measurement-device-independent quantum key distribution(MDI-QKD) can be improved not only by the protocol, but also single-photon sources. We study the behavior of MDI-QKD with statistical fluctuation using quantum blockade source. Numerical simulation for a type of 4-intensity protocol shows that, after parameter optimization, this source can improve the final key rate by 100 times compared with traditional weak coherent state sources.
- Published
- 2018
32. Measurement-device-independent quantum key distribution with source state errors and statistical fluctuation
- Author
-
Zong-Wen Yu, Xiang-Bin Wang, and Cong Jiang
- Subjects
Physics ,Protocol (science) ,Quantum Physics ,Failure probability ,FOS: Physical sciences ,Statistical fluctuations ,Quantum key distribution ,01 natural sciences ,010305 fluids & plasmas ,Measurement device ,0103 physical sciences ,Key (cryptography) ,Range (statistics) ,State (computer science) ,Statistical physics ,Quantum Physics (quant-ph) ,010306 general physics - Abstract
We show how to calculate the secure final key rate in the four-intensity decoy-state MDI-QKD protocol with both source errors and statistical fluctuations with a certain failure probability. Our results rely only on the range of only a few parameters in the source state. All imperfections in this protocol have been taken into consideration without any unverifiable error patterns., Published in PRA in March 2017. We present general results for MDIQKD with both intensity error of source and statistical fluctuation
- Published
- 2017
33. Practical measurement-device-independent quantum key distribution without vacuum sources
- Author
-
Yi-Heng Zhou, Zong-Wen Yu, Xiang-Bin Wang, and Xiaolong Hu
- Subjects
Physics ,Protocol (science) ,business.industry ,Quantum key distribution ,01 natural sciences ,010305 fluids & plasmas ,Measurement device ,0103 physical sciences ,Computer Science::Networking and Internet Architecture ,Key (cryptography) ,Electronic engineering ,Optoelectronics ,010306 general physics ,business ,Computer Science::Cryptography and Security - Abstract
Most of existing protocols for the decoy-state measurement-device-independent quantum key distribution use vacuum sources or extremely weak sources, but the laboratory cannot give real vacuum sources or precise extremely weak sources. We present a four-intensity protocol without using any of them. Our protocol gives a secure key rate close to those in the protocols with vacuum sources.
- Published
- 2017
34. Measurement-device-independent quantum key distribution with source state errors in photon number space
- Author
-
Xiang-Bin Wang, Zong-Wen Yu, and Cong Jiang
- Subjects
Physics ,Quantum Physics ,Photon antibunching ,Photon ,FOS: Physical sciences ,Quantum key distribution ,Quantum tomography ,Space (mathematics) ,01 natural sciences ,010309 optics ,Task (computing) ,Quantum mechanics ,0103 physical sciences ,Range (statistics) ,State (computer science) ,Quantum Physics (quant-ph) ,010306 general physics ,Algorithm - Abstract
The existing decoy-state MDI-QKD theory assumes the perfect control of the source states which is a an impossible task for any real setup. In this paper, we study the decoy-state MDI-QKD method with source errors without any presumed conditions and we get the final security key rate only with the range of a few parameters in the source state., Comment: Published in PRA in Dec. 2016. We present formula for the MDIQKD with an unstable source, i.e., in the case there are intensity errors. Our general formula applies to almost all types of sources, such as WCS, HSPS, the passive decoy state protocol and so on. arXiv admin note: text overlap with arXiv:1710.08211
- Published
- 2016
35. Measurement-Device-Independent Quantum Key Distribution Over a 404 km Optical Fiber
- Author
-
Wei-Jun Zhang, Zhen Wang, Hui Liu, Xiang-Bin Wang, Fei Zhou, Yi-Heng Zhou, Yingqiu Mao, Hao Chen, Xiao Jiang, Jian-Wei Pan, Ming-Qi Huang, Teng-Yun Chen, Ming-Jun Li, Zong-Wen Yu, Sijing Chen, Lixing You, Hua-Lei Yin, Qiang Zhang, and Daniel A. Nolan
- Subjects
Physics ,Quantum Physics ,Optical fiber ,business.industry ,FOS: Physical sciences ,General Physics and Astronomy ,Quantum channel ,Quantum key distribution ,01 natural sciences ,law.invention ,010309 optics ,Measurement device ,law ,ComputerSystemsOrganization_MISCELLANEOUS ,0103 physical sciences ,Computer Science::Networking and Internet Architecture ,Optoelectronics ,Quantum Physics (quant-ph) ,010306 general physics ,business ,Protocol (object-oriented programming) ,Computer Science::Cryptography and Security - Abstract
Quantum key distribution (QKD) can provide unconditional secure communication between two distant parties. Although the significance of QKD is undisputed, its feasibility has been questioned because of certain limitations in the practical application of real-life QKD systems. It is a common belief the lack of perfect single-photon source and the existence of detection loss will handicap the feasibility of QKD by creating security loopholes and distance limitations. The measurement device independent QKD (MDIQKD) with decoy-state method removes the security threats from both the imperfect single-photon source and the detection loss. Lengthening the distance and improving the key rate of QKD with such a superior method is thus the central issue in the practical application of QKD. Here, we report the results of MDIQKD over 404 km of ultralow-loss optical fibre and 311 km of standard optical fibre by employing an optimized four-intensity decoy-state method. This record-breaking implementation of MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems, more significantly, it achieves a distance that the traditional BB84 QKD would not be able to achieve with the same detection devices even with ideal single-phone sources. For the first time, our work demonstrates that with the MDIQKD method, imperfect devices can achieve better results than what ideal sources could have achieved. This work represents a significant step towards proving and developing a feasible long-distance QKD., Comment: 15 pages, 3 figures
- Published
- 2016
36. Making the decoy-state measurement-device-independent quantum key distribution practically useful
- Author
-
Xiang-Bin Wang, Yi-Heng Zhou, and Zong-Wen Yu
- Subjects
Physics ,Quantum Physics ,Decoy state ,business.industry ,FOS: Physical sciences ,Private communication ,Quantum key distribution ,01 natural sciences ,010309 optics ,Measurement device ,0103 physical sciences ,Quantum Physics (quant-ph) ,010306 general physics ,business ,Protocol (object-oriented programming) ,Delay time ,Computer network - Abstract
The relatively low key rate seems to be the major barrier to its practical use for the decoy state measurement device independent quantum key distribution (MDIQKD). We present a 4-intensity protocol for the decoy-state MDIQKD that hugely raises the key rate, especially in the case the total data size is not large. Also, calculation shows that our method makes it possible for secure private communication with {\em fresh} keys generated from MDIQKD with a delay time of only a few seconds., Typing errors corrected, presentation improved
- Published
- 2016
37. Reexamination of decoy-state quantum key distribution with biased bases
- Author
-
Zong-Wen Yu, Yi-Heng Zhou, and Xiang-Bin Wang
- Subjects
Physics ,Protocol (science) ,Decoy state ,Basis (linear algebra) ,02 engineering and technology ,State (functional analysis) ,Statistical fluctuations ,Quantum key distribution ,021001 nanoscience & nanotechnology ,01 natural sciences ,0103 physical sciences ,Key (cryptography) ,Statistical physics ,010306 general physics ,0210 nano-technology - Abstract
In order to improve the key rate of the decoy-state method, we need to jointly study yields of different bases. Given the delicate fact that pulses of the same preparation state can have different counting rates if they are measured in different bases, for example, those vacuum pulses and those single-photon pulses, existing results of decoy-state quantum key distribution using biased bases are actually flawed by assuming that they are equal. We fix this flaw through using the idea that yields of pulses prepared in different bases are the same provided that they are prepared in the same state and also measured in the same basis, for example, those single-photon pulses prepared in different bases but measured in the same basis. Based on this, we present correct formulas for the decoy-state method using biased bases. Taking the effects of statistical fluctuations into account, we then numerically study the key rates of different protocols with all parameters being fully optimized. Our result confirms the prior conclusion that the decoy-state method using biased bases can have an advantage over the symmetric protocol with unbiased bases. We obtain high key rates of our four-intensity protocol without using any vacuum source.
- Published
- 2016
38. Quantum cloning machine of a state in a belt of Bloch sphere
- Author
-
Zong-Wen Yu, Jiazhong Hu, and Xiang-Bin Wang
- Subjects
Physics ,Bloch sphere ,Cloning (programming) ,Quantum state ,Quantum mechanics ,Qubit ,Quantum operation ,Covariant transformation ,Quantum Physics ,Quantum information ,Quantum cloning ,Atomic and Molecular Physics, and Optics ,Quantitative Biology::Cell Behavior - Abstract
We analyze the problem of approximate quantum cloning when the quantum state is between two latitudes on the Bloch's sphere. We present an analytical formula for the optimized 1-to-2 cloning. The formula unifies the universal quantum cloning (UQCM) and the phase covariant quantum cloning.
- Published
- 2008
39. Improved statistical fluctuation analysis for measurement-device-independent quantum key distribution with three-intensity decoy-state method
- Author
-
Xiang-Bin Wang, Yi-Heng Zhou, and Zong-Wen Yu
- Subjects
Physics ,Quantum Physics ,Decoy state ,Computer simulation ,FOS: Physical sciences ,Quantum key distribution ,Statistical fluctuations ,Atomic and Molecular Physics, and Optics ,Quantum cryptography ,Key (cryptography) ,Statistical physics ,Quantum Physics (quant-ph) ,Quantum information science ,Intensity (heat transfer) - Abstract
We present an improved statistical fluctuation analysis for measurement device independent quantum key distribution with three-intensity decoy-state method. Taking the statistical fluctuations for different sources jointly, we present more tightened formulas for some key quantities used in calculating the secure final key. Numerical simulation shows that, given the total number of pulses $10^{12}$, our method improves the key rate by about 97\% for a distance of 50kms compared with the result given by Xu., et al. (Phys. Rev. A 89, 052333); and improves the key rate by $146\%$ for a distance of 100kms compared with the result from full optimization of all parameters but treating the statistical fluctuations traditionally, i.e., treating the fluctuations for different sources separately., 11 pages, one figure
- Published
- 2014
40. Tightened estimation can improve the key rate of measurement-device-independent quantum key distribution by more than 100%
- Author
-
Zong-Wen Yu, Yi-Heng Zhou, and Xiang-Bin Wang
- Subjects
Physics ,Measurement device ,Quantum cryptography ,Key (cryptography) ,Electronic engineering ,Quantum key distribution ,Quantum information science ,Atomic and Molecular Physics, and Optics - Published
- 2014
41. Three-intensity decoy-state method for measurement-device-independent quantum key distribution
- Author
-
Xiang-Bin Wang, Zong-Wen Yu, and Yi-Heng Zhou
- Subjects
Physics ,Quantum cryptography ,Alice and Bob ,Decoy state ,Bounding overwatch ,Quantum mechanics ,Key (cryptography) ,Quantum key distribution ,Quantum information science ,Upper and lower bounds ,Algorithm ,Atomic and Molecular Physics, and Optics ,Computer Science::Cryptography and Security - Abstract
We study the measurement-device-independent quantum key distribution (MDI-QKD) in practice with limited resources, when there are only three different states in implementing the decoy-state method. We present a tighter explicit formula to estimate the lower bound of the yield of two-single-photon pulses sent by Alice and Bob. Moreover, we show that the bounding of this yield and phase flip error of single-photon pulse pairs can be further improved by using other constraints which can be solved by a simple and explicit program. Our methods here can significantly improve the key rate and the secure distance of MDI-QKD with only three intensities.
- Published
- 2013
42. Efficient tomography of quantum-optical Gaussian processes probed with a few coherent states
- Author
-
Jiazhong Hu, Xiang-Bin Wang, Franco Nori, Adam Miranowicz, and Zong-Wen Yu
- Subjects
Physics ,Infinite set ,Quantum Physics ,Multi-mode optical fiber ,Feasible region ,FOS: Physical sciences ,Atomic and Molecular Physics, and Optics ,symbols.namesake ,Quantum process ,Quantum mechanics ,symbols ,Coherent states ,Cutoff ,Quantum Physics (quant-ph) ,Gaussian process ,Quantum - Abstract
An arbitrary quantum-optical process (channel) can be completely characterized by probing it with coherent states using the recently developed coherent-state quantum process tomography (QPT) [Lobino et al., Science 322, 563 (2008)]. In general, precise QPT is possible if an infinite set of probes is available. Thus, realistic QPT of infinite-dimensional systems is approximate due to a finite experimentally-feasible set of coherent states and its related energy-cut-off approximation. We show with explicit formulas that one can completely identify a quantum-optical Gaussian process just with a few different coherent states without approximations like the energy cut-off. For tomography of multimode processes, our method exponentially reduces the number of different test states, compared with existing methods., 6 pages, 1 figure. Some parts of this article are based on our preliminary unpublished version arXiv:1010.0472v1
- Published
- 2013
43. Decoy-state method of quantum key distribution with both source errors and statistics fluctuations
- Author
-
Huan-Hang Chi, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
Physics ,Protocol (science) ,Quantum cryptography ,Decoy state ,Signal source ,Key (cryptography) ,Statistical physics ,Quantum key distribution ,Decoy ,Atomic and Molecular Physics, and Optics - Abstract
The effects of statistical fluctuation and vacuum source fluctuation on the decoy-state method with an unstable decoy source and signal source are studied. The method is improved by a tightened estimation of the vacuum count. Compared with the existing results with an unstable vacuum source and statistical fluctuation, the results presented here have improved the key rate of the 3-intensity protocol for quantum key distribution.
- Published
- 2012
44. Entanglement-distribution maximization over one-sided Gaussian noisy channels
- Author
-
Jiazhong Hu, Xiang-Bin Wang, and Zong-Wen Yu
- Subjects
Physics ,Quantum Physics ,Quantum discord ,Gaussian ,FOS: Physical sciences ,Quantum capacity ,Quantum channel ,Quantum entanglement ,Squashed entanglement ,Atomic and Molecular Physics, and Optics ,symbols.namesake ,Separable state ,Quantum mechanics ,symbols ,Statistical physics ,Quantum Physics (quant-ph) ,Amplitude damping channel - Abstract
We present an upper bound of the entanglement evolution for two-mode Gaussian pure states under a one-sided Gaussian map. Based on this, the optimization of entanglement evolution is studied. Even if complete information about the one-sided Gaussian noisy channel does not exist, one can still maximize the entanglement distribution by testing the channel with only two specific states.
- Published
- 2010
45. A Unified Quantum NOT Gate
- Author
-
Xiang-Bin Wang, Xiaotong Ni, Leong Chuan Kwek, and Zong-Wen Yu
- Subjects
Statistics and Probability ,Physics ,Bloch sphere ,Quantum Physics ,Phase (waves) ,FOS: Physical sciences ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,Matrix multiplication ,Quantum state ,Modeling and Simulation ,Scheme (mathematics) ,Quantum mechanics ,Inverter ,Covariant transformation ,Quantum Physics (quant-ph) ,Quantum ,Mathematical Physics - Abstract
We study the feasibility of implementing a quantum NOT gate (approximate) when the quantum state lies between two latitudes on the Bloch's sphere and present an analytical formula for the optimized 1-to-$M$ quantum NOT gate. Our result generalizes previous results concerning quantum NOT gate for a quantum state distributed uniformly on the whole Bloch sphere as well as the phase covariant quantum state. We have also shown that such 1-to-$M$ optimized NOT gate can be implemented using a sequential generation scheme via matrix product states (MPS).
- Published
- 2008
46. Optimal Broadcasting of Mixed Equatorial Qubits
- Author
-
Zong-Wen, Yu, primary
- Published
- 2009
- Full Text
- View/download PDF
47. Statistical fluctuation analysis for measurement-device-independent quantum key distribution with three-intensity decoy-state method.
- Author
-
Zong-Wen Yu, Yi-Heng Zhou, and Xiang-Bin Wang
- Subjects
- *
QUANTUM fluctuations , *QUANTUM measurement , *PHASE shift keying , *QUANTUM theory , *QUANTUM information science , *QUANTUM cryptography - Abstract
We present an improved statistical fluctuation analysis for measurement-device-independent quantum key distribution with a three-intensity decoy-state method. Taking the statistical fluctuations for different sources jointly, we present more tightened formulas for some key quantities used in calculating the secure final key. Numerical simulation shows that, given the total number of pulses 1012, our method improves the key rate by about 97% for a distance of 50 km compared with the result given by Xu et al. [F. Xu et al., Phys. Rev. A 89, 052333 (2014)], and improves the key rate by 145% for a distance of 100 km compared with the result from full optimization of all parameters but treating the statistical fluctuations traditionally, i.e., treating the fluctuations for different sources separately. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
48. Tightened estimation can improve the key rate of measurement-device-independent quantum key distribution by more than 100%.
- Author
-
Yi-Heng Zhou, Zong-Wen Yu, and Xiang-Bin Wang
- Subjects
- *
QUANTUM states , *PHOTONS , *BELL'S theorem , *LINEAR programming , *TRAVELING salesman problem , *NUMERICAL analysis - Abstract
We present formulas that tighten the upper bound for the phase-flip errors in the decoy-state method by using four intensities. Our result compressed the bound to about a quarter of the known result for measurement-device-independent quantum key distribution. Based on this, we find that the key rate is improved by more than 100% given weak coherent state sources, and even more than 200% with heralded single-photon sources. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
49. Protecting quantum states from decoherence of finite temperature using weak measurement.
- Author
-
Shu-Chao Wang, Zong-Wen Yu, Wen-Jie Zou, and Xiang-Bin Wang
- Subjects
- *
QUANTUM states , *DECOHERENCE (Quantum mechanics) , *TEMPERATURE effect , *QUANTUM entanglement , *SUDDEN death - Abstract
Exposed in the nonzero temperature environment, a quantum system can both lose and gain excitations by interacting with the environment. In this work, we show how to optimally protect quantum states and quantum entanglement in such a situation based on measurement reversal from weak measurement. In particular, we present explicit formulas of protection. We find that this scheme can circumvent the entanglement sudden death in certain conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
50. Three-intensity decoy-state method for measurement-device-independent quantum key distribution.
- Author
-
Zong-Wen Yu, Yi-Heng Zhou, and Xiang-Bin Wang
- Subjects
- *
PHOTONS , *QUANTUM theory , *QUANTUM states , *BELL'S theorem , *MATHEMATICAL inequalities - Abstract
We study the measurement-device-independent quantum key distribution (MDI-QKD) in practice with limited resources, when there are only three different states in implementing the decoy-state method. We present a tighter explicit formula to estimate the lower bound of the yield of two-single-photon pulses sent by Alice and Bob. Moreover, we show that the bounding of this yield and phase flip error of single-photon pulse pairs can be further improved by using other constraints which can be solved by a simple and explicit program. Our methods here can significantly improve the key rate and the secure distance of MDI-QKD with only three intensities. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.