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Cavity electro-opto-mechanical (EOM) systems enable the microwave-optical interaction via the mechanical intermedia. By driving the electromechanical and optomechanical beam splitter interactions simultaneously, the EOM system can coherently convert the photons between microwave and optical domains bidirectionally. Here, we use this property to study a tunable dual-mode radio frequency reception, which is achieved by coherent frequency up-conversion in a two-mechanical-mode EOM system, and signal processing in an all-optical manner. A comprehensive design of EOM based dual-mode radio frequency receiver is proposed and demonstrated. We systematically analyze the realization of dual-mode radio frequency reception and verification of the dual-mode tunability. The results suggest well performance in tunable dual-mode frequency up-conversion and noise suppression. In addition, it also shows the advantages in low-power consumption, miniaturization, and massive on-chip integration. Given the latest advances on cavity electro-opto-mechanics, our scheme is feasible and can be extended to tunable multichannel multimode radio frequency reception.

We study a novel detection of radio frequency signal, which is realized by the coherent microwave-optical conversion and optical processing. An electro-opto-mechanical converter, which enables the bidirectional transduction of the information between microwave and optical domains, is performed to convert the radio frequency signal into optical photons. We demodulate the converted optical signal for the baseband information via homodyne detection. We propose a comprehensive design of radio frequency front end based on the electro-opto-mechanics, and investigate the noise characteristics, which is quantified by the noise figure. The results show that the total noise figure can be significantly suppressed to 3.155 dB. Our scheme can be extended to tunable multichannel multimode radio frequency reception with the latest advances on electro-opto-mechanics. This study opens up prospects for radio frequency sensing with coherent microwave-optical conversion.

Converting signals from the microwave to the optical domain has attracted great attention due to its potential applications in the field of quantum networks. Achieving efficient transduction is a significant yet challenging task, where a high efficiency at single photon level and low added noise are required. Electro-opto-mechanics have been proven to be efficient to convert microwave and optical photons bidirectionally. In this work, we propose and demonstrate an enhanced microwave-optical conversion in an electro-opto-mechanical system by introducing a mechanical ancilla attached the microwave resonator. Based on the ancillary electromechanical coupling, the damping rate of the microwave resonator is controlled and further leads to significant enhancement in conversion, such as the increase of conversion efficiency, broadening of conversion bandwidth and reduction of added noise. It provides a feasible approach to realize a broadband microwave-optical conversion with high efficiency. Moreover, the reduced added noise may break the limitation of quantum transduction due to the ancillary electromechanical coupling. Our scheme is also applicable and feasible for opto-mechanics and other systems to achieve practical quantum interface.

A scheme of parametrically enhanced cavity electro-opto-mechanical converter is proposed in this paper, which utilizes Josephson parametric amplifier and optical parametric amplifier. Basic principles of typical cavity electro-opto-mechanical converter and parametrically enhanced version are introduced briefly. We have probed the squeezing and microwave-optical entanglement performance of the scheme with one or both of the amplifiers. The Wigner distribution of the optical output is obtained to analyze the squeezing effect. Meanwhile, quadrature variances and time domain waveforms of output signals are compared and discussed. The results show that microwave-optical entanglement has been enhanced via nonlinear parametric effects no matter when there is one or two amplifiers. However, single mode squeezing only occurs in the cavity which the amplifier is placed in, and this squeezing effect would not transmit to another cavity which hasn’t been amplified. When both amplifiers are introduced simultaneously, each output of cavity electro-opto-mechanical converter is squeezed independently. Our research provides another way to prepare squeezed microwave or optical signal and proves that microwave-optical entanglement can be well enhanced by introducing parametric amplifiers.

Entangled microwave signal is a new quantum information resource generated in recent years. We present that entangled microwave signals can be used as the medium to realize quantum information transmission. Focusing on the divergent problem of propagation, a partial detection model based on beam splitter is established to investigate the detection efficiency and influence factors of entangled microwave signals. We analyze the relation between the entanglement degree of partial detection and detection ratio and discuss the reason that causes the reduction of entanglement degree. We give ameliorative designs of microwave signal generator and transmitter to increase the operating distance and pave the way for the application of entangled microwave signals. Keywords: Entangled microwave signals, Partial detection, Beam splitter, Entanglement degree

The basic principles for preparation and detection of continuous variable polarization entanglement in quantum optics, as well as the generalized criterion of bipartite polarization entanglement, are briefly introduced. Based on theories and experiments in quantum optics, a scheme of bipartite quantum microwave polarization entanglement is proposed and simulated. Inseparability of Stokes vector as I(Ŝ1,Ŝ2) and I(Ŝ2,Ŝ3) are obtained in order to witness the polarization entanglement in 100 MHz operation bandwidth of Josephson mixer. Furthermore, relations between inseparability I and squeezing parameter r as well as amplitude ratio Q are discussed respectively. The results show that I(Ŝ1,Ŝ2) is sensitive of the variance of Q, while I(Ŝ2,Ŝ3) seems to be sensitive of the variance of r. Meanwhile, I(Ŝ1,Ŝ2) remains above 1 in the paper, while I(Ŝ2,Ŝ3) is on the contrary well below 1. It can be concluded that Ŝ2 and Ŝ3 of Stokes vectors are inseparable, which means that output signals Êa and Êb of the scheme exhibit bipartite entanglement in polarization. The best entanglement appears at 70 MHz or so with the minimum I(Ŝ2,Ŝ3) value of 0.25. Apart from these, precision of witness for polarization entanglement and quadrature entanglement is compared. Polarization entanglement appears to be easier and more precise to witness according to our research. Keywords: Quantum microwave, Bipartite polarization entanglement, Josephson mixer, Stokes vectors, Inseparability

A method for evaluating the entanglement efficiency of dual-path entangled microwaves based on second-order correlation detection is proposed in this paper. The relationship between the squeezing degree and the entanglement efficiency in the lossless case was analyzed using the second-order interference visibility as the indicator based on measurements of the signal field strength. A loss model was established to analyze the relationship between the average thermal photons, squeezing degree, and entanglement efficiency in the lossy case. The results show that in the lossless case, a larger squeezing degree leads to a lower percentage of entangled photons, giving a lower entanglement efficiency. The entanglement efficiency first increases and then decreases with the increase of the squeezing degree in the lossy case, where the maximum achievable entanglement efficiency depends on the average thermal photons. The lower number the average thermal photons, the higher the maximum achievable entanglement efficiency, and the lower the corresponding squeezing degree. The research results provide a theoretical reference to balance the entanglement degree and entanglement efficiency of industrially-prepared dual-path entangled microwaves. Keywords: Entangled microwaves, Second-order correlation detection, Entanglement efficiency