Ultra-scalable photonics for quantum computing and networking
This research project aims to develop high-speed programmable photonic circuits compatible with cryogenic temperatures and use a complementary metal-oxide-semiconductor (CMOS) fabrication process architecture for the visible-near infrared spectrum.
Recent advances in photonic integrated circuits (PICs) technology that uses light to perform various functions found their use in applications for computation, communication, and sensing. They are essential development because they allow for integrating multiple optical components onto a single chip, leading to smaller, more efficient, and more versatile devices. One of the most critical components of PICs is Mach-Zehnder interferometers (MZIs).
MZIs are interferometers that use two parallel beams of light to interfere with each other. When these MZIs are cascaded, they form a Mach-Zehnder mesh (MZM), which can perform universal linear-optical transformations on N input/output optical modes. MZMs serve critical functions in photonic quantum information processing, quantum-enhanced sensor networks, machine learning, and other applications. We introduce a large-scale MZM platform made in a 200 mm complementary metal–oxide–semiconductor foundry, which uses aluminum nitride piezo-optomechanical actuators coupled to silicon nitride waveguides, enabling low-loss propagation with phase modulation at greater than 100 MHz in the visible–near-infrared wavelengths. Moreover, the vanishingly low hold-power consumption of the piezo-actuators enables these photonic integrated circuits to operate at cryogenic temperatures, paving the way for a fully integrated device architecture for a range of quantum applications [1-2].
a, Schematic of a four-mode programmable circuit consisting of cascaded MZIs for SU(4) operations. b, Trade space diagram of the power–reconfiguration rate for other CMOS-compatible photonic technologies and our piezo-actuated photonics. c, Microscopy images of a fully processed 200 mm wafer with insets showing the zoomed-in view of a reticle and a 4 × 4 MZM. d, Three-dimensional concept art of an MZI with piezo-optomechanical phase shifters. e, Cross-sectional diagram of our phase shifter, illustrating how an applied voltage across the piezo results in strain imparted to the optical waveguide.
Atom-control photonic integrated circuit (APIC) platform
Advancement in the laser technology has driven discoveries in atomic, molecular, and optical (AMO) physics and emerging applications, from quantum computers with cold atoms or ions to quantum networks with solid-state color centers. This progress is motivating the development of a new generation of “programmable optical control” systems, characterized by criteria,
(C1) visible (VIS) and near-infrared (IR) wavelength operation,
(C2) large channel counts extensible beyond 1000s of individually addressable atoms,
(C3) high-intensity modulation extinction,
(C4) repeatability compatible with low gate errors,
(C5) fast switching times.
We are addressing these challenges by introducing an atom control architecture based on VIS-IR photonic integrated circuit (PIC) technology. Based on a complementary metal-oxide-semiconductor (CMOS) fabrication process, this Atom-control PIC (APIC) technology meets the system requirements (C1)-(C5).
As a proof of concept, we have demonstrated a 16-channel silicon nitride-based APIC with (5.8\pm±0.4) ns response times and -30 dB extinction ratio at a wavelength of 780 nm [3].
Atom-control photonic integrated circuit (APIC) platform. a, Photograph of the full reticle. b, APIC modulator array with a modulator pitch of 420µm. c, 4×4 out-coupling and 1×16 in-coupling area. Chip detail (left) and camera image with light coupled into all ports (right). d, SEM image of the individual ring (top). Schematic cross-section of the device with piezo-stack and waveguiding layers illustrated. e, DRMZM with local in- and out-coupling gratings can be used as an alternative to the grating couplers in c. Bottom right: Illustration of setup. An SLM projects light onto the APIC, where the light is modulated and after passing through a PBS imaged onto an array of (artificial) atoms.
References
[1] High-speed programmable photonic circuits in a cryogenically compatible, visible–near-infrared 200 mm CMOS architecture, Nature Photonics volume 16, pages 59–65 (2022).
[2] High-fidelity trapped-ion qubit operations with scalable photonic modulators, arXiv: 2210.14368 (2022).
[3] Scalable photonic integrated circuits for programmable control of atomic systems, arXiv:2210.03100 (2022).
Piezo-Optomechanical Integration of Diamond Emitters
Quantum information processing would allow certain classes of problems to be solved that are effectively impossible for classical computers but tractable for quantum computers with a sufficient number of qubits and fidelity for gates and readout [1]. Scalability is extremely valuable to maturing the technology to where it is commercially viable to perform quantum information processing with many qubits. A promising candidate is the spin qubit hosted in diamond defect complexes [2]. To be able to perform quantum optics experiments with scalable platforms like photonic integrated circuits (PICs), it is necessary to develop an efficient method of interfacing between these diamond emitters and PICs in such a way that the relevant photon properties can be controlled.
References
[1] Arute, F., Arya, K., Babbush, R. et al. Quantum supremacy using a programmable superconducting processor. Nature 574, 505–510 (2019).
[2] Duan, Y., Chen, K.C., et al. A Vertically Loaded Diamond Microdisk Resonator (VLDMoRt) towards a Scalable Quantum Network. Conference on Lasers and Electro-Optics (CLEO) (2021), paper JW4L.6.