Spectral control over $\gamma$-ray echo using a nuclear frequency comb system

TL;DR

This paper theoretically investigates spectral control techniques in nuclear frequency comb systems to enhance gamma-ray echo efficiency, achieving up to 67% efficiency and simplifying implementation for gamma-ray quantum memory applications.

Contribution

It introduces spectral shaping and dynamical splitting methods to optimize gamma-ray echo efficiency in nuclear frequency comb systems, extending quantum optics to the 10keV regime.

Findings

Achieved gamma-ray echo efficiency up to 67%.

Reduced sample thickness needed for high efficiency.

Few targets suffice for good echo performance.

Abstract

Two kinds of spectral control over $\gamma$-ray echo using a nuclear frequency comb system are theoretically investigated. A nuclear frequency comb system is composed of multiple nuclear targets under magnetization (hyperfine splitting), mechanical motion (Doppler shift) or both, namely, moving and magnetized targets. In frequency domain the unperturbed single absorption line of $\gamma$-ray therefore splits into multiple lines with equal spacing and becomes a nuclear frequency comb structure. We introduce spectral shaping and dynamical splitting to the frequency comb structure respectively to optimize the use of a medium and to break the theoretical maximum of echo efficiency, i.e., 54\%. Spectral shaping scheme leads to the reduction of required sample resonant thickness for achieving high echo efficiency of especially a broadband input. Dynamical splitting method significantly advances the echo efficiency up to 67\% revealed by two equivalent nuclear frequency comb systems. We also show that using only few targets is enough to obtain good echo performance, which significantly eases the complexity of implementation. Our results extend quantum optics to 10keV regime and lay the foundation of the development of $\gamma$-ray memory.