Generation of single photons with highly tunable wave shape from a cold atomic ensemble

Abstract

The generation of ultra-narrowband, pure and storable single photons with widely tunable wave shape is an enabling step toward hybrid quantum networks requiring interconnection of remote disparate quantum systems. It allows interaction of quantum light with several material systems, including photonic quantum memories, single trapped ions and opto-mechanical systems. Previous approaches have offered a limited tuning range of the photon duration of at most one order of magnitude. Here we report on a heralded single photon source with controllable emission time based on a cold atomic ensemble, which can generate photons with temporal durations varying over three orders of magnitude up to 10 μs without a significant change of the readout efficiency. We prove the nonclassicality of the emitted photons, show that they are emitted in a pure state, and demonstrate that ultra-long photons with nonstandard wave shape can be generated, which are ideally suited for several quantum information tasks.

Photonic quantum state transfer between a cold atomic gas and a crystal

“…They propagate in the same optical mode but opposite direction than the write pulses and their polarization is set to σ + by a PBS and a quarter waveplate. The intensity and temporal wave shape of the read pulses are tailored to efficiently generate read photons with tunable waveform [33]. The read photons are emitted on the |eA → |gA transition and leave the atomic cloud in the opposite direction than the write photons due to the phase matching condition kr = kR + kW − kw, where kr, kw ( kR, kW ) represent the wave vectors of the photonic (pulse) modes.…”

Optimal photon generation from spontaneous Raman processes in cold atoms

“…If the duration of the process is short enough with respect to the atomic coherence times, and the optical depth of the sample sufficiently high, then the read photon is emitted efficiently in a well defined mode and the protocol provides a viable single photon source.Such sources have been at the core of numerous experiments during the last decade following the seminal paper of Duan, Lukin, Cirac and Zoller [3], showing how they could be used for long-distance quantum communication based on quantum repeater architectures (for reviews, see [4][5][6][7]). Recently, they have been used as quantum memories with storage times up to 200 ms [8,9] or as a source producing pure single photons with a temporal duration that can be varied over up to 3 orders of magnitude while maintaining constant efficiencies [10]. We stress that the efficiency of such a source is a critical parameter for the implementation of efficient quantum repeater architectures.…”

Efficient generation of temporally shaped photons using nonlocal spectral filtering

“…Here we consider the generation of photons with the exponentially rising temporal shape, which are required for the efficient interaction with a two-level quantum emitter in free space [8][9][10], with an ensemble of atoms [20], for coupling to a quantum memory [11,12], to an optical [21] or a superconducting resonator [26]. As a resource, we consider pairs of time-energy entangled photons with the following joint prob-ability amplitude of a single pair:…”

“…The modulation function uniquely defines the temporal shape of the heralded photon, while the outcome of the frequency-resolving detector defines the central frequency of the heralded photon [1]. Therefore, post-selection on the detected frequency is required to produce a shaped photon with the desired central frequency, which is important for the efficient interaction of the photon with a single two-level atom [8][9][10], or a quantum memory [11,12]. However, such post-selection lowers the generation rate of shaped photons and limits the applicability of this shaping method.…”