Coherent control of collective atom phase for ultralong, inversion-free photon echoes

Abstract

To overcome the fundamental limitations of the π optical pulse-induced population inversion and optical decay-caused short storage time in conventional photon echoes, a coherent control of collective atoms is studied for inversion-free, optical decay-halted photon echoes, where the constraint of photon storage time is now replaced by a spin population decay process. Using phase-controlled double rephasing, an inversion-free photon echo scheme is obtained, where no spontaneous or stimulated emission-driven quantum noise exists. Thus, the present method can be applied for ultralong quantum memories in quantum repeaters for long-distance quantum communications.

Scalable time reversal of Raman echo quantum memory and quantum waveform conversion of light pulse

“…This is a result of additional phase modulation of the irradiated echo field [43]. Here, it is worth noting other new elaborated schemes of PEQMs providing atomic rephasing without using all tools inherent in CRIB-protocol, such as the atomic frequency comb [44] and the approaches exploiting even natural IB of resonant transitions [45][46][47]. Nevertheless, it was found [48] that all these new protocols can also suffer from the loss of perfect time-reversibility by decreased quantum efficiency and fidelity for relatively broadband input light fields.…”

Understanding of Collective Atom Phase Control in Modified Photon Echoes for a Near-Perfect Storage Time-Extended Quantum Memory

“…In other words, echo E 2 could not be radiated from the medium. This fact has already been explored numerically [ 14 , 15 , 16 ] and analytically [ 17 ]. From now on, we discuss and correct critical mistakes in previous analyses [ 8 , 9 , 10 , 11 , 12 , 13 ].…”

“…Over the last decade, modified photon echo techniques have been intensively studied and applied to quantum memory applications to overcome the fundamental limitation of population inversion in conventional photon echoes, for which the population inversion excited by an optical π pulse results in quantum noises caused by spontaneous and/or stimulated emissions [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Photon echo has also been experimentally studied in a highly doped crystal Tm:YAG [ 18 ] and in ruby upon excitation through an optical fiber [ 19 ].…”

“…Recent observations of photon echoes in single [ 8 , 9 ] and double [ 10 , 11 , 12 , 13 ] rephasing photon echo schemes contradict the CCC theory but reveal coherence leakage by Gaussian light pulses, resulting in echo generations all the time, regardless of the pulse area, whose maximum efficiency reaches as high as 26% [ 22 ]. In addition to our previous studies on numerical [ 14 , 15 , 16 ] and analytical [ 17 ] approaches, herein, we discuss the CCC theory by using the commonly applied Maxwell–Bloch (MB) approach to correct the critical mistakes in previous works [ 8 , 9 , 10 , 11 , 12 , 13 ] and thus to contribute to the implementation of photon echo–based quantum memory.…”

“…The data (D), the first rephasing (R 1 ) and the second rephasing (R 2 ) pulses were resonant to the transition of to satisfy the requirements of the DR photon echo scheme [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. The control pulses, C 1 and C 2 , were resonant between states and to enable CCC [ 14 , 15 , 16 , 17 , 18 , 19 ]. Initially, all atoms of the medium were in the ground state, .…”