Quantum science and technology can offer fundamental enhancements in sensing, communications and computing. The expansion from wired to wireless links is an exciting prospect for quantum technologies. For classical technologies, the advent of phased arrays enabled directional and adaptive wireless links by manipulating electromagnetic waves over free space. Here we demonstrate a phased array system on a chip that can receive, image and manipulate non-classical light over free space. We use an integrated photonic-electronic system with more than 1000 functional components on-chip to detect squeezed light. By integrating an array of 32 sub-wavelength engineered metamaterial antennas, we demonstrate a direct free-space-to-chip interface for reconfigurable quantum links. On the same chip, we implement a large-scale array of quantum-limited coherent receivers that can resolve non-classical signals simultaneously across 32 channels. With coherent readout and manipulation of these signals, we demonstrate 32-pixel imaging and spatially configurable reception of squeezed light over free space. Our work advances wireless quantum technologies that could enable practical applications in quantum communications and sensing.
Quantum science and technology can offer fundamental enhancements in sensing, communications and computing. The expansion from wired to wireless links is an exciting prospect for quantum technologies. For classical technologies, the advent of phased arrays enabled directional and adaptive wireless links by manipulating electromagnetic waves over free space. Here we demonstrate a phased array system on a chip that can receive, image and manipulate non-classical light over free space. We use an integrated photonic-electronic system with more than 1000 functional components on-chip to detect squeezed light. By integrating an array of 32 sub-wavelength engineered metamaterial antennas, we demonstrate a direct free-space-to-chip interface for reconfigurable quantum links. On the same chip, we implement a large-scale array of quantum-limited coherent receivers that can resolve non-classical signals simultaneously across 32 channels. With coherent readout and manipulation of these signals, we demonstrate 32-pixel imaging and spatially configurable reception of squeezed light over free space. Our work advances wireless quantum technologies that could enable practical applications in quantum communications and sensing.
Emerging technologies that employ quantum physics offer fundamental enhancements in information processing tasks, including sensing, communications, and computing. Here, we introduce the quantum phased array, which generalizes the operating principles of phased arrays and wavefront engineering to quantum fields, and report the first quantum phased array technology demonstration. An integrated photonic-electronic system is used to manipulate free-space quantum information to establish reconfigurable wireless quantum links in a standalone, compact form factor. Such a robust, scalable, and integrated quantum platform can enable broad deployment of quantum technologies with high connectivity, potentially expanding their use cases to real-world applications. We report the first, to our knowledge, free-space-to-chip interface for quantum links, enabled by 32 metamaterial antennas with more than 500,000 sub-wavelength engineered nanophotonic elements over a 550 x 550 μm2 physical aperture. We implement a 32-channel array of quantum coherent receivers with 30.3 dB shot noise clearance and 90.2 dB common-mode rejection ratio that downconverts the quantum optical information via homodyne detection and processes it coherently in the radio-frequency domain. With our platform, we demonstrate 32-pixel imaging of squeezed light for quantum sensing, reconfigurable free-space links for quantum communications, and proof-of-concept entanglement generation for measurement-based quantum computing. This approach offers targeted, real-time, dynamically-adjustable free-space capabilities to integrated quantum systems that can enable wireless quantum technologies.
Fundamental physical laws dictate the performance bounds of all technologies. Over the last century, advances in nanotechnology and integrated circuits have driven the performance of communications, sensing, and computing toward these bounds. As scaling continues, classical limits are increasingly constraining further improvements. The advent of quantum technologies opens paths to overcoming some of these constraints and to building technologies that operate at the fundamental physical limits. This thesis develops a unified framework for these limits and demonstrates large-scale integrated photonic-electronic systems that approach them. In sensing, quantum phased arrays—coherent antenna arrays that transmit or receive quantum fields over free space—are introduced and demonstrated with up to 32 elements for squeezed light imaging, beamforming and beamsteering, overcoming the standard quantum limit to approach the Heisenberg limit and enabling protocols for free-space quantum sensing, quantum communications, and quantum information processing. In communications, quantum coherent transceivers are introduced and demonstrated that transmit and receive non-classical light to surpass the Shannon limit and approach the Holevo limit. In computing, large-scale crosstalk-corrected thermo-optic phase shifter arrays and a 256-element programmable photonic mesh are demonstrated, addressing the scaling challenges of integrated photonic-electronic processors. For each system, I present the underlying theory, design, experiments, and applications, and outline a vision for how these technologies can be practically deployed in the future.
Nonclassical states of light are an essential resource for many emerging quantum technologies and applications ranging from information processing, encrypted communications, and networking to sensing, metrology, and imaging. Nonlinear optical processes in solid-state materials are widely used for generating quantum light, including single photons, entangled-photon pairs, and quadrature-squeezed states. Recent advances in nonlinear photonics have enabled the functionality of benchtop nonlinear instruments to be scaled down to a single chip without sacrificing efficiency or degrading the key performance metrics. The dramatic improvement in the size, weight, power, cost, and stability enabled by photonic integrated circuits has been essential for enabling the chip-scale generation, manipulation, and detection of quantum light at a steadily increasing degree of complexity and scale. Within the last decade, the authors have seen the progression from few-component photonic circuits operating on two photons to arrays of 18 identical heralded single-photon sources and reconfigurable devices operating with more than 650 components for multidimensional entanglement and arbitrary two-photon quantum gates. In this review, the authors summarize the history and recent key technological developments of chip-scale nonlinear quantum light generation based on integrated nonlinear photonics, recent advances in heterogeneous integrated methods, and approaches for system-level integration and demonstrated applications.
Integration of quantum optical technique on-chip is crucial for large scale applications of quantum technology, which were proven in a free space environment to be superior to the corresponding classical technology. Squeezed states of light can be used for enhancing the sensitivity of quantum sensors and for fault-tolerant quantum computing. Although chip-based squeezed light generation has advanced significantly, practical impact remains limited because coupling losses between the chip and off-chip detectors destroy delicate quantum correlations, restricting the amount of observed squeezing. Here, we overcome this limitation by implementing the idea of on-chip quantum measurement with the aid of a parametric amplifier and applying it to the squeezed state generated by a silicon nitride (SiN) microring resonator. In our scheme, two matched SiN micro-rings are sequentially constructed. The first ring generates a squeezed state, whereas the second ring acts as a high-gain parametric amplifier (PA) that measures the squeezed state before the light experiences significant off-chip loss. This architecture is inherently loss-tolerant: the amplifier elevates the quantum noise well above the vacuum level, making the measurement insensitive to downstream losses. We directly observe a quantum noise reduction of 4.6 dB from the first ring, despite a chip-to-fiber coupling loss exceeding 5 dB. This work also demonstrates the first monolithic SU(1,1) interferometer with an estimated 5 dB signal-to-noise enhancement compared to traditional linear interferometers, and thus establishes a practical pathway for chip-based quantum sensors.
The work presented in this thesis is focused on experimental application and generation of continuous variable quantum correlated states of light in integrated dielectric structures. Squeezed states are among the most exploited continuous variable optical states for free-space quantum-enhanced sensing and communication protocols, but for these developments to be applicable for future technologies they must be transformed to an integrated architecture compatible with current electro-optical technology. So far only little work has been done in this direction, but two such contributions are made in this thesis: Firstly, we present proof-of-principle demonstration of interfacing squeezed light with an on-chip optomechanical resonator, demonstrating a quantum-enhanced sensitivity to the vibrations of the micromechanical object. Secondly, work on developing an integrated source of squeezed light is presented and an optimized device design is proposed. The devices have been fabricated and tested optically and preliminary interrogations of the output quantum noise have been performed.