Electric fields for light: Propagation of microwave photons along a synthetic dimension

TL;DR

This paper demonstrates a novel method of simulating particle dynamics using microwave photons in a superconducting resonator with a synthetic frequency dimension, enabling complex quantum simulations with minimal hardware complexity.

Contribution

The authors introduce a synthetic frequency dimension in microwave photonics, allowing for simplified quantum simulation of lattice models and phenomena like Bloch oscillations.

Findings

Photon wavepackets propagate in a synthetic frequency lattice.

The dispersion relation of the synthetic lattice is characterized.

Bloch oscillations are observed in the photon dynamics.

Abstract

The evenly-spaced modes of an electromagnetic resonator are coupled to each other by appropriate time-modulation, leading to dynamics analogous to those of particles hopping between different sites of a lattice. This substitution of a real spatial dimension of a lattice with a "synthetic'" dimension in frequency space greatly reduces the hardware complexity of an analog quantum simulator. Complex control and read-out of a highly multi-moded structure can thus be accomplished with very few physical control lines. We demonstrate this concept with microwave photons in a superconducting transmission line resonator by modulating the system parameters at frequencies near the resonator's free spectral range and observing propagation of photon wavepackets in time domain. The linear propagation dynamics are equivalent to a tight-binding model, which we probe by measuring scattering parameters between frequency sites. We extract an approximate tight-binding dispersion relation for the synthetic lattice and initialize photon wavepackets with well-defined quasimomenta and group velocities. As an example application of this platform in simulating a physical system, we demonstrate Bloch oscillations associated with a particle in a periodic potential and subject to a constant external field. The simulated field strongly affects the photon dynamics despite photons having zero charge. Our observation of photon dynamics along a synthetic frequency dimension generalizes immediately to topological photonics and single-photon power levels, and expands the range of physical systems addressable by quantum simulation.