Strongly Interacting Rydberg Excitations of a Cold Atomic Gas

Dudin, Y. O.; Kuzmich, A.

doi:10.1126/science.1217901

Cited by 514 publications

(603 citation statements)

References 33 publications

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“…As shown by Peyronel and co-workers 67 , such a medium converts incident coherent states of light, consisting of a Poisson distribution in photon number, into outgoing single-photon pulses by absorptive filtering of photon-number states. Related techniques allow the implementation of a deterministic singlephoton source 68 , the switching of light with light 69 , atom-photon entanglement 70 and the control of light using Rydberg polaritons 71 .…”

Section: Quantum Nonlinear Optics Through Atom-atom Interactionsmentioning

confidence: 99%

Quantum nonlinear optics — photon by photon

2014

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other. This linearity in light propagation, in combination with the high frequency and hence large bandwidth provided by waves at optical frequencies, has made optical signals the preferred method for communicating information over long distances. In contrast, the processing of information requires some form of interaction between signals. In the case of light, such interactions can be enabled by nonlinear optical processes. These processes, which are now found ubiquitously throughout science and technology, include optical modulation and switching, nonlinear spectroscopy and frequency conversion 1 , and have applications across both the physical 2 and biological 3,4 sciences.A long-standing goal in optical science has been the implementation of nonlinear effects at progressively lower light powers or pulse energies. The ultimate limit may be termed 'quantum nonlinear optics' (Box 1) -the regime where individual photons interact so strongly with one another that the propagation of light pulses containing one, two or more photons varies substantially with photon number. Although this domain is difficult to reach owing to the small nonlinear coefficients of bulk optical materials, the potential payoff is significant. The realization of quantum nonlinear optics could improve the performance of classical nonlinear devices, enabling, for example, fast energy-efficient optical transistors that avoid Ohmic heating 5 . Furthermore, nonlinear switches activated by single photons could enable optical quantum information processing and communication 6 , as well as other applications that rely on the generation and manipulation of non-classical light fields 7,8 . The challenge of making photons interactAt low optical powers, most optical materials exhibit only linear optical phenomena, such as refraction and absorption, which can be described by a complex index of refraction. However, a sufficiently intense light beam can modify a material's index of refraction, such that the light propagation becomes power-dependent. This is the essence of classical nonlinear optics (Box 1). Large optical fields are required to alter the index of refraction of conventional bulk materials because a strong nonlinear response can only be induced if the electric field of the light beam acting on the electrons is comparable to the field of the nucleus. As a result, early experimental observations of nonlinear optical phenomena, such as frequencydoubling or sum-frequency generation 9 , were achievable only after the development of powerful lasers. Advances in nonlinear optics over the past four decades have resulted in progressively more efficient nonlinear processes 10 , thus enabling the observation of nonlinear processes at lower and lower light levels. It is natural to inquire if and how these nonlinear interactions can be made so strong that they become important even at the level of individual quanta of radiation. Although this question was addressed in early theoretical studies [11][12][13] , it has become more pressing with the advent of...

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Section: Quantum Nonlinear Optics Through Atom-atom Interactionsmentioning

confidence: 99%

Quantum nonlinear optics — photon by photon

2014

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“…Our approach is to couple a light field propagating in a dispersive medium to highly excited atomic states with strong mutual interactions (Rydberg states) 13,14 . Similar to previous studies of quantum nonlinearities via Rydberg states that were based on dissipation [15][16][17][18][19] rather than dispersion 20 , we make use of electromagnetically induced transparency (EIT) to slow down the propagation of light 21 in a cold atomic gas. By operating in a dispersive regime away from the intermediate atomic resonance (Fig.…”

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confidence: 99%

Attractive photons in a quantum nonlinear medium

Firstenberg¹,

Peyronel²,

Liang³

et al. 2013

Nature

411

493

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* These authors contributed equally to this workThe fundamental properties of light derive from its constituent particles (photons) that are massless and do not interact with one another 1 . At the same time, it has been long known that the realization of coherent interactions between individual photons, akin to those associated with conventional massive particles, could enable a wide variety of unique scientific and engineering applications 2,3 . Here, by coupling light to strongly interacting atomic Rydberg states in a dispersive regime, we demonstrate a quantum nonlinear medium inside which individual photons travel as massive particles with strong mutual attraction, such that the propagation of photon pairs is dominated by a two-photon bound state 4-7 . We measure the dynamical evolution of the two-photon wavefunction using time-resolved quantum state tomography, and demonstrate a conditional phase shift 8 exceeding one radian, resulting in polarization-entangled photon pairs. Unique applications include all-optical switching, deterministic photonic quantum logic, and the generation of strongly correlated states of light 9 .Interactions between individual photons are being explored in cavity quantum electrodynamics, where a single, confined electromagnetic mode is coupled to an atomic system 10-12 . Our approach is to couple a light field propagating in a dispersive medium to highly excited atomic states with strong mutual interactions (Rydberg states) 13,14 . Similar to previous studies of quantum nonlinearities via Rydberg states that were based on dissipation 15-19 rather than dispersion 20 , we make use of electromagnetically induced transparency (EIT) to slow down the propagation of light 21 in a cold atomic gas. By operating in a dispersive regime away from the intermediate atomic resonance (Fig. 1b), where atomic absorption is low and only weakly nonlinear 22 , we realize a situation where Rydberg-atom-mediated coherent interactions between individual photons dominate the propagation dynamics of weak light pulses. Previous theoretical studies have proposed various scenarios for inducing strong interactions between individual photons 2,3,23 and for creating bound states of a few quanta 4,5,7,24 , a feature generic to strongly interacting quantum field theories. The first experimental realization of a photonic system with strong attractive interactions, including evidence for a predicted two-photon bound state, represents the main result of this work.Our experiment (outlined in Fig. 1a) makes use of an ultracold rubidium gas loaded into a dipole trap, as described previously 19 . The probe light of interest is σ + polarized, coupling the ground state |g to the Rydberg state |r via an intermediate state |e of linewidth Γ/(2π) = 6.1 MHz by means of a control field that is detuned by ∆ below the resonance frequency of the upper transition |e → |r (Fig. 1b). Under these conditions, for a very weak probe field with mean incident photon rate R i = 0.5 µs −1 , EIT is established when the probe detuning matches...

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“…using Rydberg atomic states [1], and more generally for applications in quantum information [2,3]. Recent proof-of-principle experiments along this line have been performed using samples containing ∼ 100 laser-cooled atoms held in a microscopic dipole trap [4] or in one-dimensional optical lattices [5]. As another example, a quasi-deterministic single-atom source has been recently demonstrated using light-assisted collisions in a small cold atomic ensemble [6].…”

Section: Introductionmentioning

confidence: 99%

Evaporative cooling of a small number of atoms in a single-beam microscopic dipole trap

et al. 2013

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We demonstrate experimentally the evaporative cooling of a few hundred rubidium 87 atoms in a single-beam microscopic dipole trap. Starting from 800 atoms at a temperature of 125 µK, we produce an unpolarized sample of 40 atoms at 110 nK, within 3 s. The phase-space density at the end of the evaporation reaches unity, close to quantum degeneracy. The gain in phase-space density after evaporation is 10 3 . We find that the scaling laws used for much larger numbers of atoms are still valid despite the small number of atoms involved in the evaporative cooling process. We also compare our results to a simple kinetic model describing the evaporation process and find good agreement with the data.

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Strongly Interacting Rydberg Excitations of a Cold Atomic Gas

Cited by 514 publications

References 33 publications

Quantum nonlinear optics — photon by photon

Quantum nonlinear optics — photon by photon

Attractive photons in a quantum nonlinear medium

Evaporative cooling of a small number of atoms in a single-beam microscopic dipole trap

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