The Hong–Ou–Mandel Effect With Atoms

Abstract

Controlling light at the level of individual photons has led to advances in fields ranging from quantum information and precision sensing to fundamental tests of quantum mechanics. A central development that followed the advent of single photon sources was the observation of the Hong-Ou-Mandel (HOM) effect, a novel two-photon path interference phenomenon experienced by indistinguishable photons. The effect is now a central technique in the field of quantum optics, harnessed for a variety of applications such as diagnosing single photon sources and creating probabilistic entanglement in linear quantum computing. Recently, several distinct experiments using atomic sources have realized the requisite control to observe and exploit Hong-Ou-Mandel interference of atoms. This article provides a summary of this phenomenon and discusses some of its implications for atomic systems. Transitioning from the domain of photons to atoms opens new perspectives on fundamental concepts, such as the classification of entanglement of identical particles. It aids in the design of novel probes of quantities such as entanglement entropy by combining well established tools of AMO physics -unity single-atom detection, tunable interactions, and scalability -with the Hong-Ou-Mandel interference. Furthermore, it is now possible for established protocols in the photon community, such as measurement-induced entanglement, to be employed in atomic experiments that possess deterministic single-particle production and detection. Hence, the realization of the HOM effect with atoms represents a productive union of central ideas in quantum control of atoms and photons.

Interference, spectral momentum correlations, entanglement, and Bell inequality for a trapped interacting ultracold atomic dimer: Analogies with biphoton interferometry

“…Over the past few years we have witnessed significant gains in development and implementation of experimental programs that exploit atom cooling techniques and laser-generated microtraps [5,12] or optical tweezers [22,77] in conjunction with time-of-flight and in situ measurements. Paralleling this experimental progress, advances were made in the formulation, implementation, testing, and employment of theoretical methodologies, including microscopic Hamiltonian exact-diagonalization and Hubbard-Hamiltonian modeling [18,19,[56][57][58].…”

“…(p. 239) Indeed, it took more than 20 years for this opinion to be challenged by Dehmelt [123,124]. Moreover, employing cooling and trapping techniques developed and refined since, it has become now possible to experimentally trap, manipulate, and measure a precise number of ultracold neutral atoms [5,12,22,77], providing impetus for the developments that led to our studies.…”

“…A measurement of the joint-coincidence probability [Eq. (40)] for U = 0, in a system of trapped bosonic atoms, has been reported recently [77].…”

Third-order momentum correlation interferometry maps for entangled quantal states of three singly trapped massive ultracold fermions

“…To put this development in context, we note here recent progress in the experimental processing of data and control and manipulation of ultracold atoms in colliding free-space beams or clouds (including free fall under the cloud's gravity) [10,11,23,25,[31][32][33] or in optical traps and tweezers (in situ or TOF) [34][35][36][37], which has motivated a growing number of both experimental [10,11,23,[31][32][33][34][35][36][37] and theoretical [12-15, 38, 39] studies concerning the analogies between quantum optics and matter-wave spectroscopy.…”

Atomic twin beams and violation of a motional-state Bell inequality from a phase-fluctuating quasicondensate source

“…The creation, manipulation and application of correlated twin-atoms is a topic of interest across a range of cold atoms experiments. This is driven by their potential utility in quantum technologies such as precision atom interferometry [1][2][3][4][5] and quantum simulation [6][7][8], as well as fundamental tests of quantum mechanics such as atomic EPR entanglement [9][10][11], the atomic Hong-Ou-Mandel effect [12][13][14] and demonstrations of a Bell inequality using motional degrees of freedom and massive particles [15][16][17][18][19]. Essential to each of these applications has been the ability to well characterise, both theoretically and experimentally, the nature of these atom-pairs as well as their intrinsic correlations [12,[20][21][22][23][24][25][26][27][28][29][30][31][32][33] Recent experiments involving atom-pairs have relied on protocols which can be reduced to the archetypal process of four-wave mixing: A pair of atoms in a coherent Bose-Einstein condensate (BEC) interact and are scattered into a distinct pair of modes (in terms of either spatial, motional or internal degrees of freedom) outside the condensate.…”