QCE20 Workshop on
Photonic Technologies for Quantum Information Science

Michael G. Raymer, University of Oregon
The Enabling Role of Photonics in the National Quantum Initiative
Abstract: Photonics plays a central role in moving quantum information science and technology forward, including the areas of quantum sensors, communication systems, and computers. I review the landscape and present some examples from ongoing work at the University of Oregon.

Ian Walmsley, Imperial College London
Quantum photonics: the future in a new light
Abstract: Light enables processing and transmission of information in a quantum system at ambient conditions, and with wide bandwidth. Harnessing this potential at a scale makes photonic quantum machines attractive. I will discuss the features of optical quantum interference that underpin this power, and some of the kinds of problems this enables quantum photonic processors to tackle. Further, I will outline some of the challenges facing the technology as well as some approaches to overcome them.

Stefan Preble, Rochester Institute of Technology
300mm foundry fabricated quantum photonic wafer
Abstract: In this talk, I will discuss the realization of a fully integrated quantum photonic wafer fabricated in a state-of-the-art 300mm photonic wafer foundry. The wafer consists of quantum circuits optimized for both visible (SiN) and telecommunication (Si) wavelengths. It integrates high-brightness entangled resonant photon sources and low-loss interferometers for manipulating quantum states. The circuits are being used for applications, including, high-dimensional entanglement, quantum frequency processing, quantum neural networks, and quantum programmable processors.

Stephanie Simmons, Simon Fraser University
Silicon Colour Centres
Abstract: The future global quantum internet will require high-performance matter-photon interfaces. The highly demanding technological requirements indicate that the matter-photon interfaces currently under study all have potentially unworkable drawbacks, and there is a global race underway to identify the best possible new alternative. For overwhelming commercial and quantum reasons, silicon is the best possible host for such an interface. Silicon is not only the most developed integrated photonics and electronics platform by far, isotopically purified silicon-28 has also set records for quantum lifetimes at both cryogenic and room temperatures [1]. Despite this, the vast majority of research into photon-spin interfaces has notably focused on visible-wavelength colour centres in other materials. In this talk I will introduce a variety of silicon colour centres and discuss their properties in isotopically purified silicon-28. Some of these centres have zero-phonon optical transitions in the telecommunications bands [2], some have long-lived spins in their ground states [3], and some, including the newly rediscovered T centre, have both [4].
[1] K. Saeedi, S. Simmons, J.Z. Salvail, et al. Science 342:830 (2013).
[2] C. Chartrand, L. Bergeron, K.J. Morse, et al. Phys. Rev. B 98:195201 (2018).
[3] K. Morse, R. Abraham, A. DeAbreu, et al. Science Advances 3:e1700930 (2017).
[4] L. Bergeron, C. Chartrand, A.T.K. Kurkjian, et al. https://arxiv.org/abs/2006.08793 (2020).

Jeff Young, University of British Columbia
Integrated Photonic Circuit Components for Quantum Information Processing
Abstract: Photons can be used for a variety of purposes in quantum information processing applications including sensing, imaging, communication, and computing.  In some, but not all applications, the quantum mechanical properties of discrete Foch states (e.g., indistinguishable single photons, entangled photon pairs etc.) are fundamental to the function of the quantum device.  While high-quality quantum optical sources and detectors are coming to the fore at wavelengths less than 1000 nm, there is a strong motivation to develop such components that operate at wavelengths greater than ~ 1200 nm, so that they might be integrated with silicon photonic circuits that offer a route to scalable photonic-based quantum information processing.  This talk will describe examples of circuit geometries and quantum-optical components being developed for the silicon-on-insulator platform.

Cindy Regal, JILA
Towards connecting microwave and optical photons with mechanical motion
Abstract: Superconducting qubits have become a powerful resource for the creation of arbitrary quantum states.  Yet optical links are the best way to preserve a quantum state over long distances.  I present work in which we are exploring an efficient and low-added noise link between the microwave and optical domains via the motion of a micromechanical SiN membrane.  Recent results include the demonstration of a nearly 50% efficient classical converter at dilution refrigerator temperatures, and harnessing electro-optic correlations for suppression of added thermal noise.  I will discuss general challenges of connecting these disparate domains of the electromagnetic spectrum, and how techniques to control mechanical mode spectra are key to realizing mechanically-mediated transduction.

Alp Sipahigil, Caltech
Optical photon generation from a superconducting qubit
Abstract: Superconducting circuits based on Josephson junctions emerged as a powerful platform for processing quantum information. However, these systems operate at low temperatures and microwave frequencies, and require a coherent interface with optical photons to transfer quantum information across long distances. In this talk, I will present our recent experiments demonstrating quantum transduction of a superconducting qubit excitation to an optical photon. I will describe how we use mesoscopic mechanical oscillators in their quantum ground states to convert single photons from microwave frequencies to the optical domain. I will conclude by discussing the prospects of this approach for realizing future quantum networks based on superconducting quantum processors.

Andrei Faraon, Caltech
Towards optical quantum networks based on rare-earth ions and nano-photonics
Abstract: Optical quantum networks for distributing entanglement between quantum machines will enable distributed quantum computing, secure communications and new sensing methods. These networks will contain quantum transducers for connecting computing qubits to travelling optical photon qubits, and quantum repeater links for distributing entanglement at long distances. In this talk I discuss implementations of quantum hardware for repeaters and transducers using rare-earth ions, like ytterbium and erbium, exhibiting highly coherent optical and spin transitions in a solid-state environment.  We showed that single ytterbium ions in nano-photonic resonators are well suited for optically addressable quantum bits with long spin coherence, single shot readout and good optical stability. These single qubits can form the backbone of future quantum repeater networks and will be augmented by optical storage and linear processing capabilities, also implemented using rare-earth ions. Towards this end we demonstrated optical quantum storage using erbium ensembles coupled to silicon photonics, where the frequency and release time of the stored photon can be controlled using on-chip electronics. Finally, to connect the optical network to superconducting quantum computers, we develop optical to microwave quantum transducers based on rare-earth ensembles simultaneously coupled to on-chip optical and microwave superconducting resonators. I conclude by addressing the remaining challenges for interconnecting these components into future quantum networks.