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Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms1,2. Present-day photonic quantum computers3–7 have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware−software system for executing many-photon quantum circuit operations using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. The system enables remote users to execute quantum algorithms that require up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and photon number-resolving readout on all outputs. Detection of multi-photon events with photon numbers and rates exceeding any previous programmable quantum optical demonstration is made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra and graph similarity8. These demonstrations validate the platform as a launchpad for scaling photonic technologies for quantum information processing. A system for realizing many-photon quantum circuits is presented, comprising a programmable nanophotonic chip operating at room temperature, interfaced with a fully automated control system.

Optical modulation plays arguably the utmost important role in microwave photonic (MWP) systems. Precise synthesis of modulated opti- cal spectra dictates virtually all aspects of MWP system quality including loss, noise figure, linearity, and types of functionalities that can be executed. However, for such a critical function, the versatility to generate and transform analog optical modulation is severely lacking, blocking the pathways to truly unique MWP functions including ultra-linear links and low-loss high rejection filters. Here, we demonstrate a versatile radiofrequency (RF) photonic spectral shaper integrated in a silicon photonic circuit. The spectral shaper controls the two modu- lation bands generated from an electro-optic modulation process in their relative amplitude and phase, offering an enhanced versatility for microwave-photonic modulation applications. Using the spectral shaper, we show electrically tailorable modulation transformations. Fur- thermore, we show a series of unprecedented RF filtering experiments through monolithic integration of the spectral shaper with a network of reconfigurable ring resonators.

We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition edge sensors. We measure $1.0(1)$~dB of broadband quadrature squeezing (${\sim}4$~dB inferred on-chip) and $1.5(3)$~dB of photon number difference squeezing (${\sim}7$~dB inferred on-chip). Nearly-single temporal mode operation is achieved, with measured raw unheralded second-order correlations $g^{(2)}$ as high as $1.95(1)$. Multi-photon events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology., Comment: Minor revisions, and Fig. 5 corrected; Now published in Science Advances

Electrodes in close proximity to an active area of a device are required for sufficient electrical control. The integration of such electrodes into optical devices can be challenging since low optical losses must be retained to realise high quality operation. Here, we demonstrate that it is possible to place a metallic shallow phosphorus doped layer in a silicon micro-ring cavity that can function at cryogenic temperatures. We verify that the shallow doping layer affects the local refractive index while inducing minimal losses with quality factors up to 10$^5$. This demonstration opens up a pathway to the integration of an electronic device, such as a single-electron transistor, into an optical circuit on the same material platform., Comment: 6 figures

Processing of microwave signals using photonics has several key advantages for applications in wireless communications. However, to bring photonic-based microwave signal processing to the mainstream requires a reduction of the form factor. Integration is a route for achieving high-performance, low-cost, and small-footprint microwave photonic devices. A high on-chip stimulated Brillouin scattering (SBS) gain is essential for synthesizing several key functionalities for advanced integrated microwave signal processing. We have optimized our on-chip SBS platform to achieve a record on-chip gain of 52 dB. In this paper, we discuss the implications of this giant gain from the viewpoint of new enabled technologies. The giant gain can be distributed over wide frequencies, which can be exploited for the realization of reconfigurable microwave bandpass, bandstop, and multiband filters. High gain also enables the demonstration of low-threshold on-chip lasers, which can be of relevance for a low-noise radio-frequency signal generation. These wide ranges of functionalities are made possible by the breakthrough on-chip gain makes Brillouin-based microwave photonic signal processing a promising approach for real-world implementation in the near future.

Signal processing using on-chip nonlinear or linear optical effects has shown tremendous potential for RF photonic applications. Combining nonlinear and linear elements on the same photonic chip can further enable advanced functionality and enhanced system performance in a robust and compact form. However, the integration of nonlinear and linear optical signal processing units remains challenging due to the competing and demanding waveguide requirements, specifically the combination of high optical nonlinearity in single-pass waveguides, which is desirable for broadband signal processing with low linear loss and negligible nonlinear distortions required for linear signal processing. Here, we report the first demonstration of integrating Brillouin-active waveguides and passive ring resonators on the same integrated photonic chip, enabling an integrated microwave photonic notch filter with ultradeep stopband suppressions of >40 dB, a low filter passband loss of

On-chip stimulated Brillouin scattering (SBS) that results from enhanced light–sound interactions, has recently demonstrated great applicability and versatility for signal generation and manipulation. Progress toward realizing fully integrated Brillouin photonic circuits is promising; however, the control and routing of on-chip optical waves requires non-reciprocal elements such as circulators, which is challenging and adds complexity. Here, a circulator-free Brillouin photonic planar waveguide circuit which eliminates the need for separate non-reciprocal elements is demonstrated. Backward inter-modal Brillouin scattering (BIBS) is used in a planar photonic integrated circuit, for the first time, to provide Brillouin processing capability in a multi-modal waveguide, conveniently allowing for the separation of counter-propagating pump and signal using passive integrated mode-selective filters. Using an As2S3–Si hybrid multi-modal photonic circuit, inter-optical-mode energy transfer with a Brillouin gain coefficient of 280 m−1W−1 is experimentally demonstrated, representing two orders of magnitude enhancement compared to conventional optical fibers. This on-chip BIBS circuit allows for independent routing of pump and signal waves, showing resilience to the cross talk. The experimental demonstrations provide an important basis for achieving fully integrated Brillouin photonic circuits without requiring on-chip circulators and fine spectral filtering, opening a new dimension for studying spatial-dependent photon–phonon nonlinear dynamics.

The last few years have seen major progress in harnessing on-chip photon-phonon interactions, leading to a wide range of demonstrations of new functionalities. Utilizing not only the optical response of a nonlinear waveguide - but also acoustic resonances - enables the realization of microwave devices with unprecedented performance, otherwise hard to achieve in all-optical processing schemes or electronically. Here, we overview on-chip stimulated Brillouin scattering (SBS) with special emphasis on microwave sources and microwave signal processing schemes. We review the different material platforms and structures for on-chip SBS, ranging from chalcogenide rib waveguides to hybrid silicon/silicon-nitride structures, high-Q photonic-phononic silica microresonators, and suspended silicon nanowires. We show that the paradigm shift in SBS research - from long length of fibers to chip-scale devices - is now moving toward fully integrated photonic-phononic CMOS chips.

Recent advances in design and fabrication of photonic-phononic waveguides have enabled stimulated Brillouin scattering (SBS) in silicon-based platforms, such as under-etched silicon waveguides and hybrid waveguides. Due to the sophisticated design and more importantly high sensitivity of the Brillouin resonances to geometrical variations in micro- and nano-scale structures, it is necessary to have access to the localized opto-acoustic response along those waveguides to monitor their uniformity and maximize their interaction strength. In this work, we design and fabricate photonic-phononic waveguides with a deliberate width variation on a hybrid silicon-chalcogenide photonic chip and confirm the effect of the geometrical variation on the localized Brillouin response using a distributed Brillouin measurement., 5 pages, 4 figures

We propose a novel squeezed light source capable of meeting the stringent requirements of continuous variable quantum sampling. Using the effective $\chi_2$ interaction induced by a strong driving beam in the presence of the $\chi_3$ response in an integrated microresonator, our device is compatible with established nanophotonic fabrication platforms. With typical realistic parameters, squeezed states with a mean photon number of 10 or higher can be generated in a single consistent temporal mode at repetition rates in excess of 100MHz. Over 15dB of squeezing is achievable in existing ultra-low loss platforms.

© 2017 Optical Society of America. We theoretically investigate lasing due to stimulated Brillouin scattering in integrated ring resonators. We give analytic expressions and numerical calculations for the lasing threshold for rings in the presence of for both linear and nonlinear loss. We demonstrate the operation of the ring in the different regimes of amplification and lasing, and show how these regimes depend on the coupling to the ring and on the nonlinear parameters. In the case of nonlinear losses, we find that there can exist an upper threshold to the lasing regime where the losses are dominated by free-carrier absorption. We also find that nonlinear losses can inhibit Brillouin lasing entirely for certain ranges of coupling parameters, and we show how the correct ranges of coupling parameters can be calculated and optimized for the design of integrated Brillouin lasers.

Integrated microwave photonics has strongly emerged as a next-generation technology to address limitations of conventional RF electronics for wireless communications. High-resolution RF signal processing still remains a challenge due to limitations in technology that offer sub-GHz spectral resolution, in particular at high carrier frequencies. In this paper, we present an on-chip high-resolution RF signal processor, capable of providing high-suppression spectral filtering, large phase shifts and ns-scale time delays. This was achieved through tailoring of the Brillouin gain profiles using Stokes and anti-Stokes resonances combined with RF interferometry on a low-loss photonic chip with strong opto-acoustic interactions. Using an optical power of

Stimulated Brillouin scattering (SB S) is a strong nonlinear interaction between the incident pump photons and the acoustic phonons in a guiding structure [1]. This results in the scattering of light from the pump field to the Stokes field which is frequency-shifted by ∼10 GHz. SBS has been extremely useful in a number of applications: ultra-narrow bandwidth laser, sensing, slow and fast-light, microwave signal processing, and ns scale light signal storage [2]. A number of geometries that can be used to harness SBS such as fibers, embedded waveguides, suspended waveguides and resonators in various materials such as silica, chalcogenide, silicon, calcium fluoride [2]. Off all the platforms, As2S3 waveguide devices have been demonstrated to be the most suitable for integrated efficient SBS [3]. While silicon offers CMOS compatibility, it suffers from multiphoton absorption and free-carrier absorption, which affects the SBS performance [4]. Furthermore, extra processing is required for fabricating suspended nanowires, which makes it hard to make longer lengths [5]. Chalcogenide glasses have demonstrated both large Kerr and SBS nonlinearity and very low two photon absorption at 1.5μm pump. Previously, the SBS gain of 23dB in As2S3 was reported [3]. In addition, chalcogenide waveguides can be fabricated on a CMOS compatible platform could result in a hybrid chalcogenide-silicon platform for enabling opto-electronic integration of applications based on SBS and Kerr nonlinearity [6].

A range of unique capabilities in optical and microwave signal processing and generation have been demonstrated using stimulated Brillouin scattering (SBS). The need to harness SBS in mass-manufacturable integrated circuits has led to a focus on silicon-based material platforms. Remarkable progress in silicon-based Brillouin waveguides has been made, but results have been hindered by nonlinear losses present at telecommunications wavelengths. Here, we report on a new approach to surpass this issue through the integration of a high Brillouin gain material, As2S3, onto a silicon-based chip. We fabricated a compact spiral device within a silicon circuit, achieving an order-of-magnitude improvement in Brillouin amplification. To establish the flexibility of this approach, we fabricated a ring resonator with free spectral range precisely matched to the Brillouin shift, enabling the first demonstration, to our knowledge, of Brillouin lasing in a planar integrated circuit. Combining active photonic components with the SBS devices shown here will enable the creation of compact, mass-manufacturable optical circuits with enhanced functionalities.

A bandstop radio frequency (RF) filter can enhance the capabilities of RF communication systems by removing unwanted signal components such as distortion, or interference. In modern cognitive radio systems, frequency agile filters are desired to block interferers with dynamically changing frequencies and powers. These filters should be tunable over a broad frequency range, and they should be capable of suppressing very strong signals with a high resolution. To simultaneously meet these requirements with traditional RF filters are highly challenging. Microwave photonic (MWP), a technology that primary deals with the generation, distribution, and processing of high speed RF signals using photonic techniques and components, is promising for creating frequency agile RF filters. However, traditional MWP filters are lacking the high resolution and peak suppression exhibited by state-of-the-art RF electrical filters. We recently introduced a new class of MWP notch filter which is free from this limitation. This scheme allowed the creation of anomalously high suppression MWP notch filter from virtually any kind of optical resonance, irrespective of its type (gain or absorption), or its magnitude. This enabled, for the first time, simultaneous optimization of the MWP filter resolution, peak attenuation, and frequency tuning range. In this paper, we present the analysis of notch filter response creation using the novel sideband processing technique. We then show the applicability of this technique to a wide range of optical filters. We compare simulated and experimental results of the notch filter response created using three types of optical filter commonly used in MWP signal processing, namely stimulated Brillouin scattering (SBS), an integrated optical ring resonator (ORR), and a phase-shifted fiber Bragg-grating (FBG).

Demonstration of continuously tunable delay, low- noise lasers, dynamically controlled gratings, and optical phase shifting using the stimulated Brillouin scattering (SBS) process has lead to the emergence of SBS as a promising technology for microwave photonics. On-chip realization of SBS enables photonic integration of microwave photonic signal processing and offers significantly enhanced performance and improved efficiency. On-chip stimulated Brillouin scattering is reviewed in the context of slow-light based tunable delay, low-noise narrow linewidth lasers and filtering for integrated microwave photonics. A discussion on key material and device properties, necessary to enable on-chip Brillouin scattering using both the single-pass and resonator geometry, is presented along with an outlook for photonic integration of microwave signal processing and gener- ation in other platforms.

Wavelength-scale SBS waveguides are enabling novel on-chip functionalities. The micro- and nano-scale SBS structures and the complexity of the SBS waveguides require a characterization technique to monitor the local geometry-dependent SBS responses along the waveguide. In this work, we experimentally demonstrate detection of longitudinal features down to 200$\mu$m on a silicon-chalcogenide waveguide using the Brillouin optical correlation domain analysis (BOCDA) technique. We provide simulation and analysis on how multiple acoustic and optical modes and geometrical variations influence the Brillouin spectrum., Comment: 8 pages, 6 figures

In this paper, we present our recent results in the area of microwave photonics. Integrated microwave photonic bandpass and bandstop filters were realized using stimulated Brillouin scattering (SBS). Our recent breakthrough in the fabrication of chalcogenide waveguides has allowed us to achieve an on-chip SBS gain of >40 dB, enabling for the first time the tailoring of the SBS response well beyond the intrinsic linewidth (~30 MHz). An electrical comb generated by an arbitrary waveform generator was modulated onto an optical carrier to generate a broadened pump which via the SBS effect created a flat and rectangular bandpass filter response in the RF domain. Controlling the number of pump lines allowed bandwidth reconfigurability from 30 MHz to 440 MHz. The measured selectivity and the passband ripple were >20 dB and

Microwave photonic filters tunable up to 30 GHz are realized on a chip using stimulated Brillouin scattering. Tailoring of the pump allows bandwidth reconfigurability from 50MHz to 440MHz with a pass band ripple of

We present the first functional signal processing device based on stimulated Brillouin scattering from a silicon nanowire. We use only 0.98dB SBS gain to create a tunable RF notch filter with an ultrahigh 48dB suppression.

We fabricated a nonlinear loss engineered silicon-chalcogenide hybrid waveguide and experimentally demonstrated TPA reduction. Additionally, we showed a five-fold improvement in the figure of merit compared to standard silicon nanowire.

We discuss the processing of RF signals using integrated stimulated Brillouin scattering. Bandpass and bandstop filters with wide reconfigurability and tuning are demonstrated. Furthermore, through the concept of RF interferometry, lossless phase amplification is demonstrated.

We demonstrate a record high Brillouin gain in a silicon chip through hybrid integration. Negligible nonlinear losses lead to a net gain amplification of 18.5 dB in a compact (0.3 mm2) 5.7cm As2S3 spiral.

We show the first functional signal processing device based on forward stimulated Brillouin scattering from a silicon nanowire. We harness 1dB of SBS gain to create a high performance, energy efficient microwave photonic notch filter. The filter possess 48dB of suppression, 98 MHz linewidth, and is tunable within a 6 GHz bandwidth. This demonstration represents a significant advance in integrated microwave photonics with potential applications in on-chip microwave signal processing and establish the foundation towards the first CMOS-compatible high performance RF photonic filter.

Microwave photonic cancellation notch filters have been shown capable of achieving ultra-high suppressions, making them an attractive candidate for on-chip signal processing. Their operation, based on destructive interference in the electrical domain, requires precise control of the phase and amplitude of the optical modulation sidebands. To date, this was attainable only through the use of dual-parallel Mach-Zehnder modulators which suffer from bias drifts that prevent stable filter operation. Here we propose a new cancellation filter topology with ease of control and enhanced stability using a bias-free phase modulator and a reconfigurable optical processor as the modulation sidebands spectral shaper.

We demonstrate the first, to the best of our knowledge, functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip stimulated Brillouin scattering gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high-performance RF photonic filter.

Instantaneous frequency measurement (IFM) of microwave signals is a fundamental functionality for applications ranging from electronic warfare to biomedical technology. Photonic techniques, and nonlinear optical interactions in particular, have the potential to broaden the frequency measurement range beyond the limits of electronic IFM systems. The key lies in efficiently harnessing optical mixing in an integrated nonlinear platform, with low losses. In this work, we exploit the low loss of a 35 cm long, thick silicon waveguide, to efficiently harness Kerr nonlinearity, and demonstrate the first on-chip four-wave mixing (FWM) based IFM system. We achieve a large 40 GHz measurement bandwidth and record-low measurement error. Finally, we discuss the future prospect of integrating the whole IFM system on a silicon chip to enable the first reconfigurable, broadband IFM receiver with low-latency., 13 pages, 7 figures

Here we show the first chip-based RF photonic band-stop filter with ultra-high suppression, high resolution, and 1-30 GHz frequency tuning. This record performance was achieved using an ultra-low Brillouin gain from a compact photonic chip

We present the first functional signal processing device based on stimulated Brillouin scattering from a silicon nanowire. We use only 0.98dB SBS gain to create a tunable RF notch filter with an ultrahigh 48dB suppression.

We demonstrate a scheme for minimising the insertion loss of an RF photonic filter, by exploiting the phase response of stimulated Brillouin scattering. We achieve a filter with high suppression, tunable bandwidth and low loss.

We report a technique to simultaneously optimize the peak rejection and the resolution of a radiofrequency photonic notch filter based on a silicon nitride ring resonator.

We review recent demonstration of stimulated Brillouin scattering in a chalcogenide photonic chip and its application to optical and microwave signal processing tasks. The interaction between light and sound via stimulated Brillouin scattering (SBS) was exploited in chalcogenide photonic circuits to achieve on-chip SBS slow and fast light, microwave photonic filters, and dynamic gratings using travelling-wave geometry. Using a ring-resonator geometry, photonic-chip based Brillouin laser was demonstrated. © 2013 SPIE.

Harnessing nonlinear optical effects in a photonic chip scale has been proven useful for a number of key applications in optical communications. Microwave photonics can also benefit from the adoption of such a technology, creating a new concept of nonlinear integrated microwave photonics. Here, we discuss the potential of on-chip nonlinear processing towards the creation of robust and multifunctional microwave photonic (MWP) processors. We also highlight key recent results in the field, including frequency agile MWP filters and ultra-wideband signal generators., 5 pages, 3 figures, invited paper at 2013 IEEE Topical Meeting on Microwave Photonics

We report a simple technique in microwave photonic (MWP) signal processing that allows the use of an optical filter with a shallow notch to exhibit a microwave notch filter with anomalously high rejection level. We implement this technique using a low-loss, tunable Si3N4 optical ring resonator as the optical filter, and achieved an MWP notch filter with an ultra-high peak rejection > 60 dB, a tunable high resolution bandwidth of 247-840 MHz, and notch frequency tuning of 2-8 GHz. To our knowledge, this is a record combined peak rejection and resolution for an integrated MWP filter., 8 pages, 5 figures

We report the first integrated tunable microwave photonic notch filter based on on-chip stimulated Brillouin scattering. The notch filter has a high-resolution with 3-dB and 6-dB bandwidths of 126 MHz and 78 MHz, respectively. The filter has a notch depth of 20 dB, and the notch frequency can be continuously tuned over a range of 2 8 GHz, which is limited only by the current measurement setup.

We report an ultrahigh resolution, tunable RF photonic notch filter with > 55 dB of suppression, achieved with less than 1 dB of SBS gain in a 6.5-cm chalcogenide photonic chip.

We report a novel class microwave photonic (MWP) notch filter with a very narrow isolation bandwidth (10 MHz), an ultrahigh stopband rejection (> 60 dB), a wide frequency tuning (1-30 GHz), and flexible bandwidth reconfigurability (10-65 MHz). This record performance is enabled by a new concept of sidebands amplitude and phase controls using an electro-optic modulator and an optical filter. This new concept enables energy efficient operation in active MWP notch filters, and opens up the pathway to enable low-power nanophotonic devices as high performance RF filters., 4 pages, 5 figures

We experimentally investigate four-wave mixing and nonlinear losses in low-loss 3 μm thick silicon strip waveguides. Adiabatic bends allow for single-mode operation in an ultra-compact 35 cm long spiral. The waveguides exhibited reduced nonlinear losses due to the large mode area of 2.75 μmsup2/sup. The nonlinear coefficient γ was measured as 5.5 msup-1/sup Wsup-1/sup. These features, along with the low propagation loss of 0.17 dB/cm, enable large idler power generation at 1550 nm.

An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple

Microwave photonic cancellation notch filters have been shown capable of achieving ultra-high suppressions independently from the strength of optical resonant filter they use, making them an attractive candidate for on-chip signal processing. Their operation, based on destructive interference in the electrical domain, requires precise control of the phase and amplitude of the optical modulation sidebands. To date, this was attainable only through the use of dual-parallel Mach-Zehnder modulators which suffer from bias drifts that prevent stable filter operation. Here we propose a new cancellation filter topology with ease of control and enhanced stability using a bias-free phase modulator and a reconfigurable optical processor as the modulation sidebands spectral shaper. We experimentally verify the long term stability of the novel filter topology through continuous real-time monitoring of the filter peak suppression over 24 hours.

This paper gives an overview of the applications of on-chip stimulated Brillouin scattering (SBS) in RF photonic signal processing, including for high extinction notch filtering, tunable phase shifter, instantaneous frequency measurement, and bandwidth-reconfigurable signal processing.

Low phase noise lasers are used throughout many applications including precision metrology [1], and pure microwave synthesis [2], among others. Stimulated Brillouin scattering (SBS), a coherent interaction between photons and phonons, is capable of spectrally purifying optical sources to sub-Hz levels [3]. Previous demonstrations of Brillouin lasers have been limited to fiber based systems or micro-resonators which use tapered fibers or prisms to couple to external setups, preventing wafer scale integration and mass production.

We report a distributed Brillouin scattering measurement in a silicon-chalcogenide hybrid platform with a controlled width variation. We confirm 2 mm spatial resolution using Brillouin optical correlation domain analysis (BOCDA) technique in the waveguide.

We demonstrate the first tunable microwave photonic filter based on stimulated Brillouin scattering in a silicon nanowire. We use the low on-chip SBS gain to create a notch with 48dB of suppression and 98MHz linewidth.