Quantum interface between light and atomic ensembles

Hammerer, Klemens; Sørensen, Anders S.; Polzik, E. S.

doi:10.1103/revmodphys.82.1041

Cited by 1,191 publications

(1,412 citation statements)

References 268 publications

Supporting

Mentioning

1,356

Contrasting

Unclassified

Order By: Relevance

“…Je suis seul ce soir avec mes rêves Je suis seul ce soir sans ton amour 41 Lyrics by Rose Noël and Jean Casanova, music by Paul Durand, sung by André Claveau…”

Section: Ferromagnetic Equilibrium States Of the Magnetunclassified

“…Moreover, rather than considering cases where quantum interference terms (the infamous "Schrödinger cat problem" [8,13,39]) vanish owing to decoherence processes [40], experimentalists have become able to control these very interferences [41], which are essential to describe the physics of quantum superpositions of macroscopic states and to explore the new possibilities offered by quantum information [22,42]. Examples include left and right going currents in superconducting circuits [15,43,44,45], macroscopic atomic ensembles [41] and entangled mechanical oscillators [46].…”

Section: General Features Of Quantum Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Understanding quantum measurement from the solution of dynamical models

Allahverdyan¹,

Balian²,

2013

View full text Add to dashboard Cite

The quantum measurement problem, to wit, understanding why a unique outcome is obtained in each individual experiment, is currently tackled by solving models. After an introduction we review the many dynamical models proposed over the years for elucidating quantum measurements. The approaches range from standard quantum theory, relying for instance on quantum statistical mechanics or on decoherence, to quantum-classical methods, to consistent histories and to modifications of the theory. Next, a flexible and rather realistic quantum model is introduced, describing the measurement of the z-component of a spin through interaction with a magnetic memory simulated by a Curie-Weiss magnet, including N 1 spins weakly coupled to a phonon bath. Initially prepared in a metastable paramagnetic state, it may transit to its up or down ferromagnetic state, triggered by its coupling with the tested spin, so that its magnetization acts as a pointer. A detailed solution of the dynamical equations is worked out, exhibiting several time scales. Conditions on the parameters of the model are found, which ensure that the process satisfies all the features of ideal measurements. Various imperfections of the measurement are discussed, as well as attempts of incompatible measurements. The first steps consist in the solution of the Hamiltonian dynamics for the spin-apparatus density matrixD(t). Its off-diagonal blocks in a basis selected by the spin-pointer coupling, rapidly decay owing to the many degrees of freedom of the pointer. Recurrences are ruled out either by some randomness of that coupling, or by the interaction with the bath. On a longer time scale, the trend towards equilibrium of the magnet produces a final stateD(t f ) that involves correlations between the system and the indications of the pointer, thus ensuring registration. AlthoughD(t f ) has the form expected for ideal measurements, it only describes a large set of runs. Individual runs are approached by analyzing the final states associated with all possible subensembles of runs, within a specified version of the statistical interpretation. There the difficulty lies in a quantum ambiguity: There exist many incompatible decompositions of the density matrixD(t f ) into a sum of sub-matrices, so that one cannot infer from its sole determination the states that would describe small subsets of runs. This difficulty is overcome by dynamics due to suitable interactions within the apparatus, which produce a special combination of relaxation and decoherence associated with the broken invariance of the pointer. Any subset of runs thus reaches over a brief delay a stable state which satisfies the same hierarchic property as in classical probability theory; the reduction of the state for each individual run follows. Standard quantum statistical mechanics alone appears sufficient to explain the occurrence of a unique answer in each run and the emergence of classicality in a measurement process. Finally, pedagogical exercises are proposed and lessons for future works on m...

show abstract

“…Je suis seul ce soir avec mes rêves Je suis seul ce soir sans ton amour 41 Lyrics by Rose Noël and Jean Casanova, music by Paul Durand, sung by André Claveau…”

Section: Ferromagnetic Equilibrium States Of the Magnetunclassified

Section: General Features Of Quantum Measurementsmentioning

confidence: 99%

Understanding quantum measurement from the solution of dynamical models

Allahverdyan¹,

Balian²,

2013

View full text Add to dashboard Cite

show abstract

“…Non-classical entangled states of spins in atomic ensembles have been successfully demonstrated in hot Rubidium gases [12,13,14] and NV centres [29] for qubit-spin interaction in the field of quantum information. In particular, cold-atom schemes with BECs is one of the strongest candidates for a prototype of a scalable quantum information processor and is naturally fit for CV SCS schemes [30,31].…”

Section: Implementation For Entangled Scssmentioning

confidence: 99%

“…If the qubit is represented by a polarised light interacting with a hot atomic ensemble [36,12,13,14] or superconducting flux qubit connected with NV-centres [37,29], we could generate two entangled states given by a pair of (|ζ |0 + | − ζ |1 )/ √ 2. Then, if a Bell state measurement is performed in two ancillary qubits, the outcome state in two SCSs is equivalent to the ECS.…”

Section: Entangling Scss Through Spin Bs Interactionmentioning

confidence: 99%

“…Spin states have previously been considered as a way of storing a qubit (i.e., two orthogonal collective spin states are used as computational basis states of an effective qubit [12,13,14,15]) but can be naturally utilised for CV quantum information processing by creating CV entangled states in a spin system. We assume that the initial state consists of each of the N A qubits in the same pure state, an easily prepared state in principle.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Generating non-classical states from spin coherent states via interaction with ancillary spins

Dooley

Joo

Proctor

et al. 2015

Optics Communications

View full text Add to dashboard Cite

The generation of non-classical states of large quantum systems has attracted much interest from a foundational perspective, but also because of the significant potential of such states in emerging quantum technologies. In this paper we consider the possibility of generating non-classical states of a system of spins by interaction with an ancillary system, starting from an easily prepared initial state . We extend previous results for an ancillary system comprising a single spin to bigger ancillary systems and the interaction strength is enhanced by a factor of the number of ancillary spins. Depending on initial conditions, we find -by a combination of approximation and numerics -that the system of spins can evolve to spin cat states, spin squeezed states or to multiple cat states. * We also discuss some candidate systems for implementation of the Hamiltonian necessary to generate these non-classical states.

show abstract

Quantum Memory

Bashkansky¹,

Black²,

Kwolek³

et al. 2021

Wiley Encyclopedia of Electrical and Electronics Engineering

View full text Add to dashboard Cite

Quantum Memory (QM) commonly refers to a system that reversibly transfers quantum states between a material storage system and a propagating electromagnetic field. It represents a key component in quantum information science and technology. Over the past 25 years, a wide range of theoretical protocols and experimental approaches to QM has been studied. These include optical delays, mechanical resonators, topological approaches, solid state spins, trapped single atoms and ions, and atomic ensembles. New applications of QM are being investigated and discovered all the time, including quantum computation, long‐distance entanglement distribution, quantum teleportation, and long‐distance quantum key distribution. Challenges to the implementation of QM include inefficiencies in storing and recovering the quantum state, and decoherence, which usually manifests by environment‐induced dephasing. In this monograph we describe, in general terms, methods and protocols that are used in many forms of QM. We also discuss the various experimental systems in which QM has been demonstrated or proposed. Additionally, we discuss the applications of QM that have been identified and progress made in implementing those applications.

show abstract

Quantum interface between light and atomic ensembles

Cited by 1,191 publications

References 268 publications

Understanding quantum measurement from the solution of dynamical models

Understanding quantum measurement from the solution of dynamical models

Generating non-classical states from spin coherent states via interaction with ancillary spins

Quantum Memory

Contact Info

Product

Resources

About