High-speed noise-free optical quantum memory

Kaczmarek, Krzysztof T.; Ledingham, Patrick M.; Brecht, Benjamin; Thomas, S. E.; Thekkadath, G. S.; Lazo-Arjona, Oscar; Munns, J. H. D.; Poem, Eilon; Feizpour, Amir; Saunders, D. J.; Nunn, J.; Walmsley, Ian A.

doi:10.1103/physreva.97.042316

Cited by 113 publications

(77 citation statements)

References 37 publications

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“…Furthermore, the photons can be used in implementing a robust and long-lasting storage and retrieval scheme in atomic gases [17,37]-one of the next evident goals in experimental quantum hybridization. The method of utilizing a one-port analysis or a quantum eraser will be used as a further characterization step beyond a characterization in the common HongOu-Mandel experiments.…”

Section: Fig 2 Two-port Correlation ⊥mentioning

confidence: 99%

Coherence Properties of Molecular Single Photons for Quantum Networks

2018

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Quantum mechanics implies that a single photon can be in the superposition of two distant spatial modes and enable nonlocal interferences. The most vivid example is the two-photon coalescence on a 50∶50 beam splitter, known as Hong-Ou-Mandel interference. In the past decade, this experiment has been used to characterize the suitability of different single-photon sources for linear optical quantum gates. This characterization alone cannot guarantee the suitability of the photons in a scalable quantum network. As for a deeper insight, we perform a number of nonclassical interference measurements of single photons emitted by a single organic molecule that are optimized by an atomic Faraday filter. Our measurements reveal near unity visibility of the quantum interference, and a one-port correlation measurement proves the ideal Fourier limited nature of our single-photon source. A delayed choice quantum eraser allows us to observe a constructive interference between the photons, and a Hong-Ou-Mandel peak is formed additionally to the commonly observed dip. These experiments comprehensively characterize the involved photons for their use in a future quantum Internet, and they attest to the fully efficient interaction of the molecular photons with a next subsequent quantum node. They can be adapted to other emitters and will allow us to gain insights to their applicability for quantum information processing. We introduce a quality number that describes the photon's properties for their use in a quantum network; this states that effectively 97% of the utilized molecular photons can be used in a scalable quantum optical system and interact with other quantum nodes. The experiments are based on a hybridization of solid state quantum optics, atomic systems, and all-optical quantum information processing.

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Section: Fig 2 Two-port Correlation ⊥mentioning

confidence: 99%

Coherence Properties of Molecular Single Photons for Quantum Networks

2018

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“…While sharing their technical simplicity, it allows for direct detection of ideal bunching with conventional visible-range single-photon detectors, a crucial property for its feasible benchmarking. At the same time, its spectral properties allow for a direct utilization in interactions with target atomic ensembles, in which prospective tunable nonlinearities and efficient and large bandwidth light storage have been demonstrated [27,[45][46][47][48][49]. We foresee employment of the developed source for studies of optical nonlinearities in quantum regime and of effects of photon statistics on the efficiency of the nonlinear processes [13,45].…”

Section: Discussionmentioning

confidence: 98%

“…We foresee employment of the developed source for studies of optical nonlinearities in quantum regime and of effects of photon statistics on the efficiency of the nonlinear processes [13,45]. We aim for the utilization of the presented thermal light for investigation of noise properties of single-photon level optical memories based on warm atomic ensembles [46]. The degree of detected photon bunching and fidelity of the retrieved photon number distribution with the ideal Bose-Einstein statistics will allow to reveal the amount and statistical structure of memory-added noise, as the ideal photon bunching observability critically depends on the light modeness [10].…”

Section: Discussionmentioning

confidence: 99%

Generation of ideal thermal light in warm atomic vapor

et al. 2018

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We present the experimental generation of light with directly observable close-to-ideal thermal statistical properties. The thermal light state is prepared using a spontaneous Raman emission in a warm atomic vapor. The photon number statistics are evaluated by both the measurement of secondorder correlation function and by the detailed analysis of the corresponding photon number distribution, which certifies the quality of the Bose-Einstein statistics generated by a natural physical mechanism. We further demonstrate the extension of the spectral bandwidth of the generated light to hundreds of MHz domain while keeping the ideal thermal statistics, which suggests a direct applicability of the presented source in a broad range of applications including optical metrology, tests of robustness of quantum communication protocols, or quantum thermodynamics.

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“…These broadening or dephasing mechanisms are major limiting factors, particularly in the field of quantum optics with atomic ensembles [2][3][4][5][6]. For instance, the coherence time of collective excitations in atomic gasses is often limited by Doppler dephasing, hindering the performance of single-photon sources and memories [7][8][9]. As Doppler broadening is an inhomogeneous dephasing mechanism, one can potentially counteract it by introducing additional velocity-dependent shifts [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Another practical, though less studied, three-level system is the ladder configuration [23], where the intermediate state is coupled to an even higher excited state (figure 1(b)). Ladder-type systems were recently shown to be advantageous for broadband, noise-free, photon storage [7,8], and they form the basis for quantum nonlinear optics with Rydberg atoms [19]. Nevertheless, a major caveat in ladder-type systems is the residual Doppler broadening due to wavelength mismatch of the two optical transitions, which leads to significant dephasing and broadening of the two-photon resonance [24].…”

Section: Introductionmentioning

confidence: 99%

Power narrowing: counteracting Doppler broadening in two-color transitions

et al. 2019

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Doppler broadening in thermal ensembles degrades the absorption cross-section and the coherence time of collective excitations. In two photon transitions, it is common to assume that this problem becomes worse with larger wavelength mismatch. Here we identify an opposite mechanism, where such wavelength mismatch leads to cancellation of Doppler broadening via the counteracting effects of velocity-dependent light-shifts and Doppler shifts. We show that this effect is general, common to both absorption and transparency resonances, and favorably scales with wavelength mismatch. We experimentally confirm the enhancement of transitions for different low-lying orbitals in rubidium atoms and use calculations to extrapolate to high-lying Rydberg orbitals. These calculations predict a dramatic enhancement of up to 20-fold increase in absorption, even in the presence of large homogeneous broadening. More general configurations, where an auxiliary dressing field is used to counteract Doppler broadening, are also discussed and experimentally demonstrated. The mechanism we study can be applied as well for rephasing of spin waves and increasing the coherence time of quantum memories. Doppler broadening is ubiquitous in atomic and molecular spectroscopy. Atoms and molecules with different thermal velocities experience different Doppler shifts, which broaden the absorption lines and reduce their contrast [1]. Increasing the light intensity typically causes further broadening due to saturation or other powerbroadening mechanisms, such as inhomogeneous light-shifts. These broadening or dephasing mechanisms are major limiting factors, particularly in the field of quantum optics with atomic ensembles [2][3][4][5][6]. For instance, the coherence time of collective excitations in atomic gasses is often limited by Doppler dephasing, hindering the performance of single-photon sources and memories [7-9]. As Doppler broadening is an inhomogeneous dephasing mechanism, one can potentially counteract it by introducing additional velocity-dependent shifts [10][11][12][13][14]. Here we study the counteraction of Doppler broadening by velocity dependent light-shifts and identify an important class of systems where such counteraction occurs naturally, without a need for additional auxiliary fields.Coherent two-photon processes, such as Raman transitions, two-photon absorption, and electromagnetically induced transparency (EIT), are at the heart of many quantum-optics protocols, ranging from quantum light sources and memories [15][16][17][18] to sensing and quantum nonlinear optics [19]. The canonical example of a three-level system employed for these processes is the Λ configuration, where two longlived ground states are coupled via an intermediate excited state. In these systems, two-photon transitions are usually characterized by negligible residual Doppler broadening, as the nearly-degenerate transition wavelengths experience opposite Doppler shifts [20]. Particularly in a degenerate Λ system under EIT conditions, atoms at all velocities cont...

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High-speed noise-free optical quantum memory

Cited by 113 publications

References 37 publications

Coherence Properties of Molecular Single Photons for Quantum Networks

Coherence Properties of Molecular Single Photons for Quantum Networks

Generation of ideal thermal light in warm atomic vapor

Power narrowing: counteracting Doppler broadening in two-color transitions

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