Preparing narrow velocity distributions for quantum memories in room-temperature alkali-metal vapors

Abstract

Quantum memories are a crucial technology for enabling large-scale quantum networks through synchronisation of probabilistic operations. Such networks impose strict requirements on quantum memory, such as storage time, retrieval efficiency, bandwidth, and scalability. On-and offresonant ladder protocols on warm atomic vapour platforms are promising candidates, combining efficient high-bandwidth operation with low-noise on-demand retrieval. However, their storage time is severely limited by motion-induced dephasing caused by the broad velocity distribution of atoms comprising the vapour. In this paper, we demonstrate velocity selective optical pumping to overcome this decoherence mechanism. This will increase the achievable memory storage time of vapour memories. This technique can also be used for preparing arbitrarily shaped absorption profiles, for instance, preparing an atomic frequency comb absorption feature.

Deterministic storage and retrieval of telecom light from a quantum dot single-photon source interfaced with an atomic quantum memory

“…Challenges arise here in obtaining large-enough atom numbers for efficient light-matter interactions, as well as operating at a substantially reduced duty cycle limited by the loading and cooling steps of the trapping [e.g., 3% in ( 46 )]. Instead of cooling and trapping, optical pumping can be used to tailor the velocity distribution of the atoms into a periodic structure to enact the atomic frequency comb protocol, i.e., a Doppler-rephasing approach, as demonstrated in alkali vapors in ( 47 ) by our team. This, in principle, allows for the ORCA coherence to be read out after any time multiple of the rephasing time (of order 10 ns is readily achievable) up to the excited-state lifetime but still remains to be demonstrated.…”

Deterministic Storage and Retrieval of Telecom Quantum Dot Photons Interfaced with an Atomic Quantum Memory

“…On the other hand, the Doppler limit can be removed and the storage time of the memory increased. This can be achieved by operating the memory in a cold atomic ensemble, or by using velocity-selective pumping [42], although achieving the high optical depths required for efficient light-matter interactions with these methods represents a significant technical challenge. An alternative approach could be to introduce additional fields to map the ORCA coherence to longer-lived states with a backward read-out to facilitate Doppler rephasing [43], or to compensate for dephasing with controlled dynamic AC-Stark shifts [44].…”

Optical pumping and relaxation of atomic population in assorted conditions

“…Thus, the OD is close to zero for the F = 2 → F transition whereas it gets significantly enhanced for the F = 3 → F transition for overlapping pump and probe beam as shown in figure 3. The complete optical pumping of the atomic population from one hyperfine level to other has crucial role for realization of quantum memory [2].…”

“…The working of quantum memory in warm atomic vapour relies on the associated elastic and inelastic processes involving the sample with its surrounding [1,2]. The relative values of these processes are a crucial parameter for realization of coherent matter waves [3].…”