Optimization of photon storage fidelity in ordered atomic arrays

Abstract

A major application for atomic ensembles consists of a quantum memory for light, in which an optical state can be reversibly converted to a collective atomic excitation on demand. There exists a well-known fundamental bound on the storage error, when the ensemble is describable by a continuous medium governed by the Maxwell–Bloch equations. However, these equations are semi-phenomenological, as they treat emission of the atoms into other directions other than the mode of interest as being independent. On the other hand, in systems such as dense, ordered atomic arrays, atoms interact with each other strongly and spatial interference of the emitted light might be exploited to suppress emission into unwanted directions, thereby enabling improved error bounds. Here, we develop a general formalism that fully accounts for spatial interference, and which finds the maximum storage efficiency for a single photon with known spatial input mode into a collection of atoms with discrete, known positions. As an example, we apply this technique to study a finite two-dimensional square array of atoms. We show that such a system enables a storage error that scales with atom number Na like ∼(logNnormalafalse)2∕Nnormala2, and that, remarkably, an array of just 4 × 4 atoms in principle allows for an error of less than 1%, which is comparable to a disordered ensemble with an optical depth of around 600.

Dicke superradiance in ordered lattices: dimensionality matters

“…For example, in ordered arrays with subwavelength interatomic separation, subradiant states with an extremely enhanced lifetime emerge [12][13][14]. These can be used to guide light as "atomic waveguides" [15][16][17] or "atomic dielectrics" [18][19][20][21], and to improve the fidelity of protocols for quantum information storage [16,22,23] and metrology [24,25], among other applications. Arranging single atoms in ordered patterns has become an experimental reality [26][27][28][29][30][31][32][33][34].…”

Photon control and coherent interactions via lattice dark states in atomic arrays

“…Ordered atomic arrays with subwavelength spacing have emerged as versatile quantum many-body systems, where coherent excitation exchange between the dipoles leads to a collective response of the atomic ensemble [1,2]. The richness of the underlying interactions can be used for a wide variety of quantum applications that range from topological phases of matter [3,4], atomic clocks [5,6] and optical quantum memories [7] to the ability to modify the radiative environment of single impurities [8,9]. Atomic arrays also offer remarkable optical properties and can act as an optical mirror for incident beams of low intensities [2,10].…”

Unidirectional absorption, storage, and emission of single photons in a collectively responding bilayer atomic array

“…Subradiant states in free-space 2D arrays of atoms [1-3, 6, 8, 10, 11, 16, 18, 24, 32, 46-48] are promising for light storage due to their isolation from the environment, but, unlike in the case of 1D chains of atoms [49,50], in 2D arrays strongly subradiant modes cannot be directly driven by incident fields. Previous proposals have demonstrated how such modes can be excited in the steady state, using atomic level shifts to control the orientation of the dipoles [3,31], or by optimizing driving [51]. Besides the giant experimental subradiance of regular arrays [44,45], long-lived states have also been experimentally observed in disordered atomic clouds [52,53].…”