Coherent spin-wave processor of stored optical pulses

Abstract

A device being a pinnacle of development of an optical quantum memory should combine the capabilities of storage, inter-communication and processing of stored information. In particular, the ability to capture a train of optical pulses, interfere them in an arbitrary way and finally perform on-demand release would in a loose sense realize an optical analogue of a Turing Machine. Here we demonstrate the operation of an optical quantum memory being able to store optical pulses in the form of collective spin-wave excitations in a multi-dimensional wavevector space. During storage, we perform complex beamsplitter operations and demonstrate a variety of protocol implemented as the processing stage, including interfering a pair of spin-wave modes with 95% visibility. By engineering the phase-matching at the readout stage we realize the on-demand retrieval. The highly multimode structure of the presented quantum memory lends itself both to enhancing classical optical telecommunication as well as parallel processing of optical qubits at the single-photon level. arXiv:1808.00927v1 [quant-ph]

Spin-Wave Multiplexed Atom-Cavity Electrodynamics

“…The demonstration here, of spin-wave multiplexed cavity electrodynamics, is a significant step toward these goals.Our apparatus is complementary to an active body of ensemble multiplexing research, using both spatial and spectral degrees of freedom [13][14][15][16][17][18][19][20][21][22][23]. Recently, a spatial array of single-photon detectors has been used to resolve 665 independent spin waves in an atomic ensemble [24,25]. However, for maximum utility in a quantum network, systems such as this require dynamic routing of free-space output photons.…”

Superradiant parametric conversion of spin waves

“…4. With this detailed view we show explicitly that correlation phase-matching patters, ranging from gaussian-like shapes to tight rings can be engineered by controlling the spin-wave wavevector K. Additionally, one can imagine that even more complex patterns could be obtained by preparing the initial spin wave in a superposition in k-space or by reshaping the spin-wave spatial structure using for example ac-Stark shift [13,18,25].…”

“…In those cases the associated SWs lie between a ground state and an excited atomic state and are intermediate steps in the generation of a photon pair. More complex manipulations of those SWs, such as temporal [13][14][15][16][17] and spatial [18] mutli-SW beamsplitters demonstrated for ground-state SWs, remain elusive. Such control would allow SW-based enginieering of photon pair emission, possibly also extensible to deterministic quantum nonlinear optics based on Rydberg atoms [19].Here we show that the properties of a phase-matched cascaded atomic decay can be engineered via proper preparation of the atomic SW state.…”

“…The standard coherent two-photon decay follows by the end of which the atom returns to its ground state |g . The entire process can be viewed as a two-step spontaneous six-wave mixing (6WM) with a time delay, which overall conserves both momentum and energy.This unorthodox view leads to numerous implications, as the SW may be manipulated in various ways, including usage of magnetic [21][22][23], electric [24] and optical fields [13,18,[25][26][27]. Reshaping the SW structure will subsequently result in a modified atomic state during emission of the idler photon.…”

Photon echoes in optically dense media

“…Herein, photon echo technique [6,7] attracts an especial everlasting attention in coherent spectroscopy [7] and light pulse storage [8][9][10][11][12]. Recently, the photon echo in optically dense media opened promising opportunities for quantum storage of a large number of light pulses [13][14][15][16][17] and quantum processing [18] that determined a steady interest and elaboration of numerous protocols of photon echo based quantum memory [14,[19][20][21][22][23][24], which are important for the creation of quantum repeater [25], microwave quantum memory [26,27], etc.…”