Engineering Phonon-Qubit Interactions using Phononic Crystals

TL;DR

This paper demonstrates the design and fabrication of diamond phononic crystals with a complete phononic bandgap that suppresses phonon interactions with quantum emitters, enabling higher-temperature quantum memory operation and new quantum functionalities.

Contribution

It introduces a method to engineer phononic density of states using phononic crystals, reducing phonon-induced decoherence in solid-state quantum systems at higher temperatures.

Findings

Achieved a phononic bandgap spanning 50-70 GHz in diamond phononic crystals.

Reduced phonon-induced orbital relaxation rate by a factor of 18 at 4 Kelvin.

Suppressed phonon interactions up to 20 Kelvin.

Abstract

The ability to control phonons in solids is key for diverse quantum applications, ranging from quantum information processing to sensing. Often, phonons are sources of noise and decoherence, since they can interact with a variety of solid-state quantum systems. To mitigate this, quantum systems typically operate at milli-Kelvin temperatures to reduce the number of thermal phonons. Here we demonstrate an alternative approach that relies on engineering phononic density of states, drawing inspiration from photonic bandgap structures that have been used to control the spontaneous emission of quantum emitters. We design and fabricate diamond phononic crystals with a complete phononic bandgap spanning 50 - 70 gigahertz, tailored to suppress interactions of a single silicon-vacancy color center with resonant phonons of the thermal bath. At 4 Kelvin, we demonstrate a reduction of the phonon-induced orbital relaxation rate of the color center by a factor of 18 compared to bulk. Furthermore, we show that the phononic bandgap can efficiently suppress phonon-color center interactions up to 20 Kelvin. In addition to enabling operation of quantum memories at higher temperatures, the ability to engineer qubit-phonon interactions may enable new functionalities for quantum science and technology, where phonons are used as carriers of quantum information.