Jacob Mower

On-chip detection of non-classical light by scalable integration of single-photon detectors

Photonic-integrated circuits have emerged as a scalable platform for complex quantum systems. A central goal is to integrate single-photon detectors to reduce optical losses, latency and wiring complexity associated with off-chip detectors. Superconducting nanowire single-photon detectors (SNSPDs) are particularly attractive because of high detection efficiency, sub-50-ps jitter and nanosecond-scale reset time. However, while single detectors have been incorporated into individual waveguides, the system detection efficiency of multiple SNSPDs in one photonic circuit—required for scalable quantum photonic circuits—has been limited to <0.2%. Here we introduce a micrometer-scale flip-chip process that enables scalable integration of SNSPDs on a range of photonic circuits. Ten low-jitter detectors are integrated on one circuit with 100% device yield. With an average system detection efficiency beyond 10%, and estimated on-chip detection efficiency of 14–52% for four detectors operated simultaneously, we demonstrate, to the best of our knowledge, the first on-chip photon correlation measurements of non-classical light.

High-fidelity quantum state evolution in imperfect photonic integrated circuits

We propose and analyze the design of a programmable photonic integrated circuit for high-fidelity quantum computation and simulation. We demonstrate that the reconfigurability of our design allows us to overcome two major impediments to quantum optics on a chip: it removes the need for a full fabrication cycle for each experiment and allows for compensation of fabrication errors using numerical optimization techniques. Under a pessimistic fabrication model for the silicon-on-insulator process, we demonstrate a dramatic fidelity improvement for the linear optics CNOT and CPHASE gates and, showing the scalability of this approach, the iterative phase estimation algorithm built from individually optimized gates. We also propose and simulate a novel experiment that the programmability of our system would enable: a statistically robust study of the evolution of entangled photons in disordered quantum walks. Overall, our results suggest that existing fabrication processes are sufficient to build a quantum photonic processor capable of high fidelity operation.

Programmable dispersion on a photonic integrated circuit for classical and quantum applications

We demonstrate a large-scale tunable-coupling ring resonator array, suitable for high-dimensional classical and quantum transforms, in a CMOS-compatible silicon photonics platform. The device consists of a waveguide coupled to 15 ring-based dispersive elements with programmable linewidths and resonance frequencies. The ability to control both quality factor and frequency of each ring provides an unprecedented 30 degrees of freedom in dispersion control on a single spatial channel. This programmable dispersion control system has a range of applications, including mode-locked lasers, quantum key distribution, and photon-pair generation. We also propose a novel application enabled by this circuit - high-speed quantum communications using temporal-mode-based quantum data locking - and discuss the utility of the system for performing the high-dimensional unitary optical transformations necessary for a quantum data locking demonstration.

Programmable nanophotonic processor for arbitrary high fidelity optical transformations

We present an architecture for programmable nanophotonic processors capable of arbitrary discrete transformations for quantum and classical applications. A method to combat fabrication imperfections with high fidelity is discussed along with initial experimental results.

Quantum random walks in a programmable nanophotonic processor

Quantum random walks (QRWs) implemented in photonic media have seen significant recent attention for their applicability to problems in quantum simulation and quantum transport. However, performing statistically robust and high-fidelity studies of these problems has required either manual tuning of optical elements or the fabrication of multiple integrated photonic chips. Here, we present our recent theoretical and preliminary experimental results on the role of disorder and decoherence in QRWs implemented in a large-scale, programmable nanophotonic processor (PNP).

High-dimensional time-energy entanglement-based quantum key distribution using dispersive optics

We implement a high-dimensional quantum key distribution protocol secure against collective attacks. We transform between conjugate measurement bases using group velocity dispersion. We obtain > 3 secure bits per photon coincidence.

Low-jitter single-photon detector arrays integrated with silicon and aluminum nitride photonic chips

We present progress on a scalable scheme for integration of single-photon detectors with silicon and aluminum nitride photonic circuits. We assemble arrays of low-jitter waveguide-integrated single-photon detectors and show up to 24% system detection efficiency.

An integrated programmable quantum photonic processor for linear optics

We introduce a reconfigurable silicon quantum photonic network for implementing general linear optics transformations in the spatial mode basis. This network enables implementation of a range of quantum algorithms; we discuss the phase estimation algorithm.

Scalable single-photon detection on a photonic chip

We developed a scalable method for integrating sub-70-ps-timing-jitter superconducting nanowire single-photon detectors with photonic integrated circuits. We assembled a photonic chip with four integrated detectors and performed the first on-chip g(2)(τ)-measurements of an entangled-photon source.

On-fiber assembly of membrane-integrated superconducting-nanowire single-photon detectors

We directly assemble membrane-integrated superconducting-nanowire single- photon detectors (SNSPDs) on optical fiber-ferrule facets, yielding extremely compact, fiber-coupled SNSPD systems. Our initial demonstration shows 1% system detection efficien- cy, which can be further improved significantly.