The ability to generate and detect quantum states of light on a single integrated photonic device is essential to scale quantum photonics into useful quantum technologies. Integrating the required capabilities into complementary-metal-oxide-semiconductor compatible monolithic chips can reduce cost and unlock new functionality through miniaturisation. In this work we demonstrate a single silicon-on-insulator photonic integrated circuit for the monolithic generation and detection of quantum light on a commercially available platform that operates entirely at room temperature. Specifically, we leverage spontaneous four-wave mixing in silicon waveguides to produce squeezed light which is subsequently detected by photodiodes operating in a pulsed homodyne detector configuration on the same chip as the source. We directly measure 0.25(1) dB of squeezing, including contributions from waveguide propagation loss and detection inefficiency, and include a detailed analysis of the impact of nonlinear loss on the squeezing levels achievable using this platform.

Quantum technologies promise profound advances in communication security, sensing and computing. The underpinning hardware must be engineered to generate, manipulate and detect quantum phenomena with exceptional performance, whilst being mass-manufacturable for real-world applications. A leading approach is chip-scale quantum photonics. The continuous-variable regime for quantum optics has been exploited in a number of technologies, including the detection of gravitational waves, by operating below the standard quantum limit of the light's shot noise. The availability of room-temperature, deterministic sources and high efficiency detectors suitable for continuous-variable state generation and measurement is a compelling motivation for this particular paradigm. This review focusses on efforts to integrate sources and detectors of continuous-variable light states into chip-scale photonic integrated circuits.

We present experimental progress towards a demonstration of continuous variable distributed quantum sensing on a silicon photonic chip, utilizing an array of integrated homodyne detectors to perform entanglement enhanced phase sensing and entanglement verification.

Low loss and high-speed processing of photons is important to photonic quantum information technologies. The speed with which quantum light generation can be modulated impacts the clock rate of photonic quantum computers, the data rate of quantum communication and applications of quantum enhanced radio-frequency sensors. Here we use lossy carrier depletion modulators in a silicon waveguide nonlinear interferometer to modulate photon pair generation probability at 1 gigahertz (GHz) without exposing the generated photons to the phase dependent parasitic loss of the mod- ulators. The super sensitivity of nonlinear interferometers reduces power consumption compared to modulating the driving laser. This can be used for high-speed programmable nonlinearity in waveguide networks for quantum technologies and for optical quantum sensors.

For absorption imaging, optical noise is a limitation [1]. Photon counting experiments using correlated photon pair sources can achieve sub-shot noise imaging but are not scalable to high brightness [2]. While lowering the noise floor increases the signal-to-noise ratio without increasing the signal's power, enhancing the precision reduces the variance of estimates. In imaging, improved precision can lead to higher contrast images, allowing regions with similar values to be more easily distinguished due to smaller error bars [2].

We present work done on the integration of homodyne detectors onto quantum photonic chips for the measurement and characterisation of continuous variable states of light, with a focus on high speed operation. © 2025 The Author(s)

Verifying entanglement between parties is essential for creating secure quantum communication. However, finite statistics can lead to false positive outcomes in any tests for entanglement. Here, we introduce a one-sided device-independent protocol that corrects for apparent signaling effects in experimental probability distributions, caused by statistical fluctuations and experimental imperfections. We use semidefinite programming to identify the optimal inequality, for our experimental probability distribution, without resource-intensive tomography. Our protocol is numerically and experimentally analyzed in the context of random, misaligned measurements, correcting apparent signaling where necessary. Our results show a significantly higher probability of violation than existing state-of-the-art inequalities. This study demonstrates the power of semidefinite programming for entanglement verification and brings quantum networks closer to practical applications.

Site-defined electron spin control is demonstrated by heterogeneous integrating NV centres in nanodiamond with silicon foundry microelectronics. Rabi oscillations indicates fifty times lower power consumption compared to addressing with an external microwave antenna.

Complimentary metal-oxide semiconductor (CMOS) integration of quantum technology provides a route to manufacture at volume, simplify assembly, reduce footprint, and increase performance. Quantum noise–limited homodyne detectors have applications across quantum technologies, and they comprise photonics and electronics. Here, we report a quantum noise–limited monolithic electronic-photonic integrated homodyne detector, with a footprint of 80 micrometers by 220 micrometers, fabricated in a 250-nanometer lithography bipolar CMOS process. We measure a 15.3-gigahertz 3-decibel bandwidth with a maximum shot noise clearance of 12 decibels and shot noise clearance out to 26.5 gigahertz, when measured with a 9–decibel-milliwatt power local oscillator. This performance is enabled by monolithic electronic-photonic integration, which goes below the capacitance limits of devices made up of separate integrated chips or discrete components. It exceeds the bandwidth of quantum detectors with macroscopic electronic interconnects, including wire and flip chip bonding. This demonstrates electronic-photonic integration enhancing quantum photonic device performance.

Whilst holding great promise for low noise, ease of operation and networking, useful photonic quantum computing has been precluded by the need for beyond-state-of-the-art components, manufactured by the millions. Here we introduce a manufacturable platform for quantum computing with photons. We benchmark a set of monolithically-integrated silicon photonics-based modules to generate, manipulate, network, and detect photonic qubits, demonstrating dual-rail photonic qubits with $99.98\% \pm 0.01\%$ state preparation and measurement fidelity, Hong-Ou-Mandel quantum interference between independent photon sources with $99.50\%\pm0.25\%$ visibility, two-qubit fusion with $99.22\%\pm0.12\%$ fidelity, and a chip-to-chip qubit interconnect with $99.72\%\pm0.04\%$ fidelity, not accounting for loss. In addition, we preview a selection of next generation technologies, demonstrating low-loss silicon nitride waveguides and components, fabrication-tolerant photon sources, high-efficiency photon-number-resolving detectors, low-loss chip-to-fiber coupling, and barium titanate electro-optic phase shifters.

We present plans to unite sources of continuous variable quantum light and detectors on a single silicon photonics chip. This includes the extension of chip based homodyne detection to the pulsed regime.

We present plans for performing continuous variable distributed quantum sensing on a silicon photonic chip. Linear functions of four integrated phase shifters will be measured with entanglement enhanced precision.

Implementing CVQKD using integrated photonics presents many advantages, such as small form factor, and the ability to mass manufacture at a high volume with a lost cost, by making use of mature electronics manufacturing technologies. Another significant advantage of using integrated photonics is for implementing CV-QKD receivers. By making use of integrated photodiodes with integrated amplification electronics it is possible to achieve high-performance wideband (GHz) homodyne detectors [1], using standard telecoms electronics at negligible cost ($10s). Increasing the detector bandwidths allows for faster baud rates, and therefore faster key rates [2]. In this work we implement a hybrid integrated photonic/electronic circuit design to demonstrate an integrated photonic CV-QKD receiver with a bandwidth of approximately 1.4GHz and our work towards making use of the design to implement a CV-QKD system with GHz baud rates. This represents an improvement in bandwidth of 2 orders of magnitude over previous chip-based CV-QKD experiments where the bandwidth of the detector was 10MHz. [2]

Nitrogen-vacancy (NV) centres in diamond show great promise for quantum computing, where photonic entanglement can be generated using long-lived optically-active spins [1]. A quantum processor would require a large number of interconnected NV centres, and an integrated platform becomes necessary for control and routing. Benefits of integration include nanophotonic cavities with ultra-small mode volumes [2], multilayer electronics, and use of existing integrated quantum photonic components and architectures. Pick-and-place methods have been adopted to combine diamond microchiplets with aluminium nitride [3]. Photonic and spin properties has also been measured in nanodiamond encapsulated in optimised silicon nitride (SiNx) [4]. However, challenges remain to interface diamond with photonics in a scalable and manufacturable process. In particular, the need to identify and manipulate stochastically located emitters requires precise and time-intensive confocal microscopy.

Complimentary metal-oxide-semiconductor (CMOS) compatible quantum technology enables scalable integration with the classical readout and control electronics needed to build quantum computers. Homodyne detectors have applications across quantum technologies including quantum computers, and they comprise photonics and electronics. Here we report a quantum noise limited monolithic electronic-photonic integrated homodyne detector, with an overall footprint of $80~\mu\mathrm{m} \times 220~\mu\mathrm{m}$, fabricated in a 250~nm lithography bi-polar CMOS process. By monolithic integration of the electronics and photonics, overall capacitance is suppressed -- this is the main bottleneck to high bandwidth measurement of quantum light. We measure a 3~dB bandwidth of 19.8~GHz and a maximum shot noise clearance of 15~dB. This exceeds bandwidth limits of detectors with macroscopic electronic interconnects, including wirebonding and flip-chip bonding. This demonstrates CMOS electronic-photonic integration enhancing performance of quantum photonics.

The compatibility of silicon photonics and silicon electronics allows for the development monolithic devices to meet the scale and performance required for quantum technologies such as quantum information processing. We present a monolithic electronic-photonic homodyne detector with a bandwidth of 19.8 GHZ. This outperforms any previous demonstrations and is directly attributable to the monolithic integration that limits the parasitic capacitance typical from packaging and interfacing multiple integrated circuits.

As a measure of the 'closeness' of two quantum states, fidelity plays a fundamental role in quantum information theory. Fidelity estimation protocols try to strike a balance between information gleaned from an experiment, and the efficiency of its implementation, in terms of the number of states consumed by the protocol. Here we adapt a previously reported optimal state verification protocol (Phys. Rev. Lett. 120, 170502, 2018) for fidelity estimation of two-qubit states. We demonstrate the protocol experimentally using a fully-programmable silicon photonic two-qubit chip. Our protocol outputs significantly smaller error bars of its point estimate in comparison with another widely-used estimation protocol, showing a clear step forward in the ability to estimate the fidelity of quantum states produced by a practical device.

Low loss and high speed processing of photons is central to architectures for photonic quantum information. High speed switching enables non-deterministic photon sources and logic gates to be made deterministic, while the speed with which quantum light sources can be turned on and off impacts the clock rate of photonic computers and the data rate of quantum communication. Here we use lossy carrier depletion modulators in a silicon waveguide nonlinear interferometer to modulate photon pair generation at 1~GHz without exposing the generated photons to the phase dependent parasitic loss of the modulators. The super sensitivity of nonlinear interferometers reduces power consumption compared to modulating the driving laser. This can be a building block component for high speed programmabile, generalised nonlinear waveguide networks.