Entanglement between light and an optical atomic excitation

Li, L.; Dudin, Y. O.; Kuzmich, A.

doi:10.1038/nature12227

Cited by 192 publications

(192 citation statements)

References 31 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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“…array of cavities [27,28], atoms within a cavity [29], and Rydberg atoms in an optical lattice [30][31][32][33]. Recently, it was pointed that [34], an imaginary transverse field may be implemented by optically pumping a qubit state into the auxiliary state.…”

Section: Summary and Discussionmentioning

confidence: 99%

Finite-temperature quantum criticality in a complex-parameter plane

Song

2015

Phys. Rev. A

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A conventional quantum phase transition (QPT) occurs not only at zero temperature, but also exhibits finite-temperature quantum criticality. Motivated by the discovery of the pseudo-Hermiticity of non-Hermitian systems, we explore the finite-temperature quantum criticality in a non-Hermitian PT -symmetric Ising model. We present the complete set of exact eigenstates of the non-Hermitian Hamiltonian, based on which the mixed-state fidelity in the context of biorthogonal bases is calculated. Analytical and numerical results show that the fidelity approach to finite-temperature QPT can be extended to the non-Hermitian Ising model. This paves the way for experimental detection of quantum criticality in a complex-parameter plane.

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“…We furthermore proceed to demonstrate strong Rydberg blockade between two, spatially separated ensemble qubits. Together with the recent demonstration of entanglement between a Rydberg excited ensemble and a propagating photon [13] these results establish a path towards both local and remote entanglement of arrays of ensemble qubits, which will enable enhanced quantum repeater architectures [14]. …”

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confidence: 99%

Coherence and Rydberg Blockade of Atomic Ensemble Qubits

et al. 2015

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We demonstrate |W state encoding of multi-atom ensemble qubits. Using optically trapped Rb atoms the T2 coherence time is 2.6(3) ms forN = 7.6 atoms and scales approximately inversely with the number of atoms. Strong Rydberg blockade between two ensemble qubits is demonstrated with a fidelity of 0.89(1) and a fidelity of ∼ 1.0 when postselected on control ensemble excitation. These results are a significant step towards deterministic entanglement of atomic ensembles.PACS numbers: 42.50.Dv, 32.80.Rm Qubits encoded in hyperfine states of neutral atoms are a promising approach for scalable implementation of quantum information processing [1]. While a qubit can be encoded in a pair of ground states of a single atom, it is also possible to encode a qubit, or even multiple qubits, in an N atom ensemble by using Rydberg blockade to enforce single excitation of one of the qubit states [2,3]. Ensemble qubits have several interesting features in comparison to single atom qubits. Using an array of traps it is simpler to prepare many ensemble qubits with N ≥ 1 for each ensemble, than it is to prepare an array with exactly one atom in each trap which remains an outstanding challenge [4][5][6]. In addition, a |W state ensemble qubit encoding is maximally robust against loss of a single atom [7], which can be remedied with error correction protocols [8], while atom loss is a critical error for single atom qubits. Furthermore an ensemble encoding facilitates strong coupling between atoms and light, an essential ingredient for quantum networking protocols [9] and atomic control of photonic interactions in Rydberg blockaded ensembles [10]. As the atomlight coupling strength grows with the number of atoms, recent experiments[10], [11] and theory proposals [12] are based on ensembles with N > 100. We are focused here on studying the physics of ensembles for computational qubits and therefore work with smaller ensembles with up to N ∼ 10 atoms.In this letter we demonstrate and study the coherence and interactions of atomic ensemble qubits. We measure the T 2 coherence time of ensemble qubits achieving a ratio of coherence time to single qubit π rotation time of ∼ 2600. We furthermore proceed to demonstrate strong Rydberg blockade between two, spatially separated ensemble qubits. Together with the recent demonstration of entanglement between a Rydberg excited ensemble and a propagating photon[13] these results establish a path towards both local and remote entanglement of arrays of ensemble qubits, which will enable enhanced quantum repeater architectures [14].

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Entanglement between light and an optical atomic excitation

Cited by 192 publications

References 31 publications

Quantum nonlinear optics — photon by photon

Quantum nonlinear optics — photon by photon

Finite-temperature quantum criticality in a complex-parameter plane

Coherence and Rydberg Blockade of Atomic Ensemble Qubits

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