arXiv subjects

Jonathan C. F. Matthews

Publications and source records attributed to Jonathan C. F. Matthews.

At least 19 recordsLinked to original sources

arXiv2026

Continuous variable distributed quantum sensing in integrated photonics

Distributed quantum sensing is an emerging application of quantum networking, where entangled probe states are employed to sense combinations of delocalized parameters with enhanced precision relative to using separable states. Squeezed states of light are a prime resource for experimental demonstrations of entanglement-enhanced sensing, because they can be generated and entangled deterministically. Existing distributed quantum sensing experiments have been fundamentally limited in scalability due to their bulk-optic architectures. Meanwhile, integrated photonics provides a scalable and compact platform for quantum sensors. Here we demonstrate entanglement-enhanced sensing of linear functions of four phase shifts in an integrated photonic circuit. We find an entanglement-enhanced precision of 0.199(16) dB below the shot noise limit compared to 0.041(18) dB for separable states. A four-mode entangled state is generated on-chip with entanglement verification and phase sensing also performed on-chip with an array of four integrated homodyne detectors.

quant-ph↗

arXiv2026

Generation and detection of squeezed light on a single silicon photonic chip

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.

quant-ph↗

arXiv2025

Correcting for finite statistics effects in a quantum steering experiment

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 analysed 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 work demonstrates the power of semidefinite programming for entanglement verification and brings quantum networks closer to practical applications.

quant-ph↗

arXiv2023

Fidelity estimation of quantum states on a silicon photonic chip

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.

quant-ph↗

arXiv2023

GHz configurable photon pair generation from a silicon nonlinear interferometer

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.

quant-ph↗

arXiv2023

A Bi-CMOS electronic-photonic integrated circuit quantum light detector

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 $80~μ\mathrm{m} \times 220~μ\mathrm{m}$, 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.

quant-ph↗

arXiv2023

Sub-μm axial precision depth imaging with entangled two-colour Hong-Ou-Mandel microscopy

The quantum interference of two wavelength-entangled photons overlapping at a beamsplitter results in an oscillating interference pattern. The frequency of the beat note is dependent on the wavelength separation of the entangled photons but is robust to wavelength scale perturbations that can limit the practicality of standard interferometry. Here we use two-colour entanglement interferometry to evaluate the variation in thickness of a semi-transparent sample in combination with two-dimensional raster scanning. The axial precision and the dynamic range of the microscope are actively controlled by adjusting the wavelength separation of the entangled photon pairs. Sub-$μm$ precision is reported using up to $12.3~nm$ of detuning and $\sim10^4$ detected photon pairs.

quant-ph↗

arXiv2023

Heterogeneous integration of solid state quantum systems with a foundry photonics platform

Diamond colour centres are promising optically-addressable solid state spins that can be matter-qubits, mediate deterministic interaction between photons and act as single photon emitters. Useful quantum computers will comprise millions of logical qubits. To become useful in constructing quantum computers, spin-photon interfaces must therefore become scalable and be compatible with mass-manufacturable photonics and electronics. Here we demonstrate heterogeneous integration of NV centres in nanodiamond with low-fluorescence silicon nitride photonics from a standard 180 nm CMOS foundry process. Nanodiamonds are positioned over pre-defined sites in a regular array on a waveguide, in a single post-processing step. Using an array of optical fibres, we excite NV centres selectively from an array of six integrated nanodiamond sites, and collect the photoluminescence (PL) in each case into waveguide circuitry on-chip. We verify single photon emission by an on-chip Hanbury Brown and Twiss cross-correlation measurement, which is a key characterisation experiment otherwise typically performed routinely with discrete optics. Our work opens up a simple and effective route to simultaneously address large arrays of individual optically-active spins at scale, without requiring discrete bulk optical setups. This is enabled by the heterogeneous integration of NV centre nanodiamonds with CMOS photonics.

quant-ph↗

arXiv2022

Estimating the concentration of chiral media with bright squeezed light

The concentration of a chiral solution is a key parameter in many scientific fields and industrial processes. This parameter can be estimated to high precision by exploiting circular birefringence or circular dichroism present in optically active media. Using the Quantum Fisher information formalism, we quantify the performance of Gaussian probes in estimating the concentration of chiral analytes. We find that bright-polarization squeezed state probes provide a quantum advantage over equally bright classical strategies that scales exponentially with the squeezing factor for a circularly birefringent sample. Four-fold precision enhancement is achievable using state-of-the-art squeezing levels and intensity measurements.

quant-ph↗

arXiv2022

Advantage of Coherent States in Ring Resonators over Any Quantum Probe Single-Pass Absorption Estimation Strategy

Quantum states of light have been shown to enhance precision in absorption estimation over classical strategies. By exploiting interference and resonant enhancement effects, we show that coherent-state probes in all-pass ring resonators can outperform any quantum probe single-pass strategy even when normalized by the mean input photon number. We also find that under optimal conditions coherent-state probes equal the performance of arbitrarily bright pure single-mode squeezed probes in all-pass ring resonators.

quant-ph↗

arXiv2021

Shot-Noise Limited Homodyne Detection for MHz Quantum Light Characterisation in the 2 μm Band

Characterising quantum states of light in the 2 $μm$ band requires high-performance shot-noise limited detectors. Here, we present the characterisation of a homodyne detector that we use to observe vacuum shot-noise via homodyne measurement with a 2.07 $μm$ pulsed mode-locked laser. The device is designed primarily for pulsed illumination. It has a 3 dB bandwidth of 13.2 MHz, total conversion efficiency of 58% at 2.07 $μm$ and a common-mode rejection ratio of 48 dB at 39.5 MHz. The detector begins to saturate at 1.8 mW with 9 dB of shot-noise clearance at 5 MHz. This demonstration enables the characterisation of megahertz-quantum optical behaviour in the 2 $μm$ band.

quant-ph↗

arXiv2021

Roadmap on Integrated Quantum Photonics

Integrated photonics is at the heart of many classical technologies, from optical communications to biosensors, LIDAR, and data center fiber interconnects. There is strong evidence that these integrated technologies will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying laser and optical quantum technologies, with the required functionality and performance, can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration and a dramatic reduction in optical losses have enabled benchtop experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. The reduction in size, weight, power, and improvement in stability that will be enabled by QPICs will play a key role in increasing the degree of complexity and scale in quantum demonstrations. In the next decade, with sustained research, development, and investment in the quantum photonic ecosystem (i.e. PIC-based platforms, devices and circuits, fabrication and integration processes, packaging, and testing and benchmarking), we will witness the transition from single- and few-function prototypes to the large-scale integration of multi-functional and reconfigurable QPICs that will define how information is processed, stored, transmitted, and utilized for quantum computing, communications, metrology, and sensing. This roadmap highlights the current progress in the field of integrated quantum photonics, future challenges, and advances in science and technology needed to meet these challenges.

quant-ph↗

arXiv2020

9~GHz measurement of squeezed light by interfacing silicon photonics and integrated electronics

Photonic quantum technology can be enhanced by monolithic fabrication of both the underpinning quantum hardware and the corresponding electronics for classical readout and control. Together, this enables miniaturisation and mass-manufacture of small quantum devices---such as quantum communication nodes, quantum sensors and sources of randomness---and promises the precision and scale of fabrication required to assemble useful quantum computers. Here we combine CMOS compatible silicon and germanium-on-silicon nano-photonics with silicon-germanium integrated amplification electronics to improve performance of on-chip homodyne detection of quantum light. We observe a 3 dB bandwidth of 1.7 GHz, shot-noise limited performance beyond 9 GHz and minaturise the required footprint to 0.84 mm. We use the device to observe quantum squeezed light, from 100 MHz to 9 GHz, generated in a lithium niobate waveguide. This demonstrates that an all-integrated approach yields faster homodyne detectors for quantum technology than has been achieved to-date and opens the way to full-stack integration of photonic quantum devices.

quant-ph↗

arXiv2020

A practical model of twin-beam experiments for sub-shot-noise absorption measurements

Quantum-intensity-correlated twin beams of light can be used to measure absorption with precision beyond the classical shot-noise limit. The degree to which this can be achieved with a given estimator is defined by the quality of the twin-beam intensity correlations, which is quantified by the noise reduction factor. We derive an analytical model of twin-beam experiments, incorporating experimental parameters such as the relative detection efficiency of the beams, uncorrelated optical noise, and uncorrelated detector noise. We show that for twin beams without excessive noise, measured correlations can be improved by increasing the detection efficiency of each beam, notwithstanding this may unbalance detection efficiency. However, for beams with excess intensity or other experimental noise, one should balance detection efficiency, even at the cost of reducing detection efficiency -- we specifically define these noise conditions and verify our results with statistical simulation. This has application in design and optimization of absorption spectroscopy and imaging experiments.

quant-ph↗

arXiv2019

Quantum Absorbance Estimation and the Beer-Lambert Law

The utility of transmission measurement has made it a target for quantum enhanced measurement strategies. Here we find if the length of an absorbing object is a controllable variable, then via the Beer-Lambert law, classical strategies can be optimised to reach within 83% of the absolute quantum limit. Our analysis includes experimental losses, detector noise, and input states with arbitrary photon statistics. We derive optimal operating conditions for both classical and quantum sources, and observe experimental agreement with theory using Fock and thermal states.

quant-ph↗

arXiv2019

Designing quantum experiments with a genetic algorithm

We introduce a genetic algorithm that designs quantum optics experiments for engineering quantum states with specific properties. Our algorithm is powerful and flexible, and can easily be modified to find methods of engineering states for a range of applications. Here we focus on quantum metrology. First, we consider the noise-free case, and use the algorithm to find quantum states with a large quantum Fisher information (QFI). We find methods, which only involve experimental elements that are available with current or near-future technology, for engineering quantum states with up to a 100-fold improvement over the best classical state, and a 20-fold improvement over the optimal Gaussian state. Such states are a superposition of the vacuum with a large number of photons (around $80$), and can hence be seen as Schrödinger-cat-like states. We then apply the two most dominant noise sources in our setting -- photon loss and imperfect heralding -- and use the algorithm to find quantum states that still improve over the optimal Gaussian state with realistic levels of noise. This will open up experimental and technological work in using exotic non-Gaussian states for quantum-enhanced phase measurements. Finally, we use the Bayesian mean square error to look beyond the regime of validity of the QFI, finding quantum states with precision enhancements over the alternatives even when the experiment operates in the regime of limited data.

quant-ph↗

arXiv2019

Quantum Optical Metrology of Correlated Phase and Loss

Optical absorption measurements characterize a wide variety of systems from atomic gases to \emph{in-vivo} diagnostics of living organisms. Here we study the potential of non-classical techniques to reduce statistical noise below the shot-noise limit in absorption measurements with concomitant phase shifts imparted by a sample. We consider both cases where there is a known relationship between absorption and a phase shift, and where this relationship is unknown. For each case we derive the fundamental limit and provide a practical strategy to reduce statistical noise. Furthermore, we find an intuitive correspondence between measurements of absorption and of lossy phase shifts, which both show the same scope for precision enhancement. Our results demonstrate that non-classical techniques can aid real-world tasks with present-day laboratory techniques.

quant-ph↗

arXiv2019

Passive, broadband and low-frequency suppression of laser amplitude noise to the shot-noise limit using hollow-core fibre

We use hollow-core fibre to preserve the spectrum and temporal profile of picosecond laser pulses in CBD to suppress 2.6 dB of amplitude noise at MHz noise frequencies, to within 0.01 dB of the shot-noise limit. We provide an enhanced version of the CBD scheme that concatenates circuits to suppress over multiple frequencies and over broad frequency ranges --- we perform a first demonstration that reduces total excess amplitude noise, between 2 - 6 MHz, by 85%. These demonstrations enable passive, broad-band, all-guided fibre laser technology operating at the shot-noise limit.

physics.optics↗