Process Tomography of Dynamical Decoupling in a Dense Cold Atomic Ensemble

Sagi, Yoav; Almog, Ido; Davidson, Nir

doi:10.1103/physrevlett.105.053201

Cited by 78 publications

(67 citation statements)

References 35 publications

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“…The maximum memory efficiency in this ensemble was, however, just a few per cent. A much longer coherence time of 3 s was achieved using a crossbeam dipole trap of 3 × 10 5 87 Rb atoms [24], although no memory was demonstrated in this experiment. This was recently improved on further, with a coherence time of 16 s [25].…”

Section: Introductionmentioning

confidence: 69%

Gradient echo memory in an ultra-high optical depth cold atomic ensemble

et al. 2013

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Quantum memories are an integral component of quantum repeaters-devices that will allow the extension of quantum key distribution to communication ranges beyond that permissible by passive transmission. A quantum memory for this application needs to be highly efficient and have coherence times approaching a millisecond. Here we report on work towards this goal, with the development of a 87 Rb magneto-optical trap with a peak optical depth of 1000 for the D2 F = 2 → F = 3 transition using spatial and temporal dark spots. With this purpose-built cold atomic ensemble we implemented the gradient echo memory (GEM) scheme on the D1 line. Our data shows a memory efficiency of 80 ± 2% and coherence times up to 195 µs, which is a factor of four greater than previous GEM experiments implemented in warm vapour cells.

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Section: Introductionmentioning

confidence: 69%

Gradient echo memory in an ultra-high optical depth cold atomic ensemble

et al. 2013

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“…Here we consider the usage of dynamical decoupling techniques [31][32][33][34] for quantum metrology. These techniques have been shown to be applicable in the context of storage or for the realization of quantum gates [35,36], and are nowadays widely used in various experimental settings [37][38][39][40][41][42][43][44][45]. We show that with the help of ultra-fast control operations that act locally on the system qubits, one can effectively decouple the system from its environment and fully protect it against decoherence effects, while at the same time maintaining its sensing capabilities and its quantum advantage in metrology.…”

Section: Introductionmentioning

confidence: 94%

Dynamical decoupling leads to improved scaling in noisy quantum metrology

2016

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We consider the usage of dynamical decoupling in quantum metrology, where the joint evolution of system plus environment is described by a Hamiltonian. We show that by ultra-fast unitary control operations acting locally only on system qubits, noise can be eliminated while the desired evolution is only reduced by at most a constant factor, leading to Heisenberg scaling. We identify all kinds of noise where such an approach is applicable. Only noise that is generated by the Hamiltonian to be estimated itself cannot be altered. However, even for such parallel noise, one can achieve an improved scaling as compared to the standard quantum limit for any local noise by means of symmetrization. Our results are also applicable in other schemes based on dynamical decoupling, e.g. the generation of highfidelity entangling gates.

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“…There exist more sophisticated methods to enhance the qubit storage time which are able to take temporal correlations into account. A formal description of this techniques is known as dynamical decoupling which has already been demonstrated in various physical systems [47][48][49][50][51][52][53]. For a given noise spectrum an optimal pattern of echo pulses can be determined to maximize the phase coherence.…”

Section: Errors In the Qubit Memorymentioning

confidence: 99%

A quantum information processor with trapped ions

et al. 2013

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Quantum computers hold the promise to solve certain problems exponentially faster than their classical counterparts. Trapped atomic ions are among the physical systems in which building such a computing device seems viable. In this work we present a small-scale quantum information processor based on a string of 40 Ca + ions confined in a macroscopic linear Paul trap. We review our set of operations which includes non-coherent operations allowing us to realize arbitrary Markovian processes. In order to build a larger quantum information processor it is mandatory to reduce the error rate of the available operations which is only possible if the physics of the noise processes is well understood. We identify the dominant noise sources in our system and discuss their effects on different algorithms. Finally we demonstrate how our entire

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Process Tomography of Dynamical Decoupling in a Dense Cold Atomic Ensemble

Cited by 78 publications

References 35 publications

Gradient echo memory in an ultra-high optical depth cold atomic ensemble

Gradient echo memory in an ultra-high optical depth cold atomic ensemble

Dynamical decoupling leads to improved scaling in noisy quantum metrology

A quantum information processor with trapped ions

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