Optical locking for quantum memory and communication

Artur V. Gleim

Alexander I. Lvovsky, Barry C. Sanders, Wolfgang Tittel

Byoung Seung HAM

Unlike slow-light-based quantum memories, photon echoes offer the benefit of high speed and wide bandwidth. Over the last decade, the rephasing mechanism of photon echoes has been studied for quantum memories to overcome fundamental limitations in photon echoes, such as population inversion and low retrieval efficiency. Although these limitations have been overcome in modified photon echo schemes, photon storage time is still too short to apply it to long-distance quantum communications. For long-distance quantum communications, ultralong photon storage time of the order of seconds is needed to implement quantum repeaters. In this review article, challenging techniques for ultralong photon storage are presented, where ultralong storage is obtained via a coherence conversion process between optical and spin states by using an optical locking technique. To remove population-inversion-caused quantum noise, a double rephasing scheme is addressed, where rephasing-pulse-caused population inversion hinders photon echoes for quantum memory applications.

K. F. Reim, Joshua Nunn, Virginia O. Lorenz +5 more

Takeshi Kondo, Seiho Shindo, Daisuke Yoshida +5 more

Abstract To implement quantum repeaters for long-distance quantum communications, frequency stabilization is necessary for coupling telecommunication wavelength photons with quantum memories that operate in the visible region. Here, a narrow-linewidth optical frequency comb for frequency stabilization is developed through phase-locking to an iodine-stabilized Nd:YAG laser using high-speed servo control. Subsequently, we phase lock a Pr 3+ :Y 2 SiO 5 (Pr:YSO) quantum memory control laser to the developed optical frequency comb for linewidth transfer. The obtained linewidth (3.1 kHz) and frequency stability (1.84 × 10 −12 at an average time of 0.01 s) are sufficient for multimode storage in Pr:YSO quantum memory.

Byoung Seung HAM

A novel method of multi-bit quantum optical data storage is presented, where the storage time can be lengthened far beyond the spin phase-decay time in a reversible spin inhomogeneous system excited by consecutive resonant Raman optical data pulses. The ultralong storage time is obtained by an optical population locking mechanism of modified rephasing process. This gives potentials to quantum repeaters utilizing quantum memories for long distance quantum communications, in which ultralong storage time plays a major role.