Volkan Gurses

The Holevo limit bounds the channel capacity of a communication channel in which information is encoded in quantum states in a Hilbert space at the transmitter and decoded using quantum measurements at the receiver. Saturating the Holevo limit requires quantum-limited transceivers that either generate quantum states of light or employ quantum-limited measurements. Here, we demonstrate an integrated photonic-electronic quantum-limited coherent receiver (QRX) achieving 14.0 dB shot noise clearance (SNC), 520 μW knee power, 2.57 GHz 3-dB bandwidth, 3.50 GHz shot-noise-limited bandwidth, and 90.2 dB common-mode rejection ratio (CMRR). We scale this design to a 32-channel QRX array with median 26.6 dB SNC, and automatic CMRR correction yielding a median 76.8 dB CMRR at minimum. Using the integrated QRX and fiber-optic transmitter, we measure 0.15 ± 0.01 dB of squeezing below the shot noise limit, limited by off-chip losses. We propose a squeezed light communication scheme that can surpass the Shannon limit, with a path toward the Holevo limit.

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 × 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.