Quantum dynamics of microwave photons in synthetic frequency dimension

TL;DR

This paper demonstrates the control and observation of single-photon quantum dynamics in a synthetic frequency lattice using superconducting circuits, enabling advanced quantum simulations and photon manipulations.

Contribution

It introduces a method to realize and measure quantum states and dynamics of single photons in a reconfigurable synthetic frequency lattice with superconducting circuits.

Findings

Observation of single-photon quantum random walks

Demonstration of Bloch oscillations at the single-photon level

Implementation of nonadiabatic, unidirectional frequency conversion

Abstract

Synthetic frequency dimension offers a powerful approach to simulate lattice models and control photon dynamics. However, extending this concept into the quantum regime, particularly at the single-photon level, has remained challenging in photonic platforms. Here, we demonstrate quantum-state initialization and detection of single-photon evolutions within a synthetic frequency lattice by integrating a superconducting qubit with a 16-meter aluminum coaxial cable. A tunable superconducting quantum interference device (SQUID)-based modulator is employed to synthesize lattice couplings and artificial gauge fields. We observe single-photon quantum random walks and Bloch oscillations, as well as nonadiabatic, unidirectional frequency conversion under rapid temporal modulation of the lattice Hamiltonian, together with band-structure measurements. The lattice connectivity can be readily reconfigured to construct higher-dimensional lattices using multiple drive tones. Our results establish superconducting quantum circuits as a versatile platform for programmable Hamiltonians and extensible synthetic lattices with flexible single-photon control.