Thermodynamics of Bose-Einstein-condensed clouds using phase-contrast imaging

Meppelink, R.; Rozendaal, R.; Koller, Sonja; Vogels, J. M.; Straten, P. van der

doi:10.1103/physreva.81.053632

Cited by 68 publications

(76 citation statements)

References 17 publications

(37 reference statements)

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“…By measuring the phase shift via interference, the state of the BEC can be inferred. The PCI measurement does not destroy the atomic condensate, it can be applied repeatedly [42,43] on the same atomic sample. This also amounts to an estimate of S z , but is not a strong measurement and instead results in some dephasing of the coherence between the levels [44].…”

Section: Experimental Implementationmentioning

confidence: 99%

Macroscopic quantum information processing using spin coherent states

Byrnes

Rosseau

Khosla

et al. 2015

Optics Communications

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Previously a new scheme of quantum information processing based on spin coherent states of two component Bose-Einstein condensates was proposed (Byrnes et al. Phys. Rev. A 85, 40306(R)). In this paper we give a more detailed exposition of the scheme, expanding on several aspects that were not discussed in full previously. The basic concept of the scheme is that spin coherent states are used instead of qubits to encode qubit information, and manipulated using collective spin operators. The scheme goes beyond the continuous variable regime such that the full space of the Bloch sphere is used. We construct a general framework for quantum algorithms to be executed using multiple spin coherent states, which are individually controlled. We illustrate the scheme by applications to quantum information protocols, and discuss possible experimental implementations. Decoherence effects are analyzed under both general conditions and for the experimental implementation proposed.

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Section: Experimental Implementationmentioning

confidence: 99%

Macroscopic quantum information processing using spin coherent states

Byrnes

Rosseau

Khosla

et al. 2015

Optics Communications

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“…In contrast to abruptly changing the scattering length [26], sinusoidal modulation enables the controlled excitation of a single mode at a specific frequency. In addition, by using this method, a coexisting thermal component will be minimally excited by the mean-field coupling to the normal gas [27,28]. In the case of a multispecies experiment, resonant modulation of the scattering length of one species will not necessarily excite the others, depending on the details of other Feshbach resonances present in the system [29].…”

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confidence: 99%

Collective excitation of a Bose-Einstein condensate by modulation of the atomic scattering length

Pollack

Dries²,

Hulet³

et al. 2010

Phys. Rev. A

101

113

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We excite the lowest-lying quadrupole mode of a Bose-Einstein condensate by modulating the atomic scattering length via a Feshbach resonance. Excitation occurs at various modulation frequencies, and resonances located at the natural quadrupole frequency of the condensate and at the first harmonic are observed. We also investigate the amplitude of the excited mode as a function of modulation depth. Numerical simulations based on a variational calculation agree with our experimental results and provide insight into the observed behavior. Collective excitation of a Bose-Einstein condensate (BEC) is an essential diagnostic tool for investigating properties of the ultracold quantum state. Fundamental information about condensate dynamics can be determined from observations of collective modes [1][2][3], including the effects of temperature [4][5][6], and the dimensionality of the system [7]. In addition, the interplay between these modes and external agents, such as random potentials [8,9], lattices [10,11], as well as other atoms [12][13][14][15][16], can be investigated. Examining the excitation spectrum of the BEC allows for a detailed comparison with theoretical models [17][18][19][20] and related quantum systems such as superfluid helium [21,22] and superconductors [23,24].Generically, a collective excitation is generated by the modification of the trapping potential of the condensate [25]. One convenient method is to apply a sudden magnetic field gradient, thereby shifting the center of the trap and exciting a dipole oscillation about the trap center. One may also suddenly change the curvature of the trap to excite quadrupole modes. The lowest-lying m = 0 quadrupole mode is characterized by out-of-phase axial and radial oscillations.If the condensate is not the only occupant of the trap (i.e., there exists a thermal component or another species of atoms) then the other atoms may also be excited through these processes. The evolution of a collective excitation can therefore be complicated because the multiple components may affect damping or induce frequency shifts of the oscillation [12][13][14][15][16]. Therefore, modulating the trap, although an extremely useful tool for an isolated condensate, can be cumbersome when the system to be studied is multispecied. An alternative approach is to excite the condensate alone, leaving the other occupants of the trap untouched.In this work, we demonstrate the excitation of the lowestlying quadrupole mode in a BEC of 7 Li by modulating the atomic scattering length via a magnetic Feshbach resonance. In contrast to abruptly changing the scattering length [26], sinusoidal modulation enables the controlled excitation of a single mode at a specific frequency. In addition, by using this method, a coexisting thermal component will be minimally excited by the mean-field coupling to the normal gas [27,28]. In the case of a multispecies experiment, resonant modulation of the scattering length of one species will not necessarily excite the others, depending on the details of other F...

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“…By measuring the phase shift via interference, the state of the BEC can be inferred. Because the PCI measurement does not destroy the atomic condensate, it can be applied repeatedly [21,22] nique is a useful resource for information readout in several proposed applications of ultra-cold atomic systems to metrology [23,24], quantum information and processing [25,26]. Other methods [27][28][29] also use a feedback mechanism to achieve greater control over the backaction induced by the measurement.…”

mentioning

confidence: 99%

Theory of Single-Shot Phase Contrast Imaging in Spinor Bose-Einstein Condensates

Ilo-Okeke

Byrnes

2014

Phys. Rev. Lett.

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We introduce a theoretical framework for single-shot phase contrast imaging (PCI) measurements of spinor Bose-Einstein condensates. Our model allows for the simple calculation of the quantum backaction resulting from the measurement, and the amount of information that is read out. We find that there is an optimum time Gτ ∼ 1/N for the light-matter interaction (G is the ac Stark shift frequency, N is the number of particles in the BEC), where the maximum amount of information can be read out from the BEC. A universal information-disturbance tradeoff law ǫF ǫG ∝ 1/N 2 is found where ǫF is the amount of backaction and ǫG is the estimation error. The PCI measurement can also be found to be a direct probe of the quantum fluctuations of the BEC, via the noise of the PCI signal.PACS numbers: 03.75. Dg, 37.25.+k, 03.75.Mn Quantum mechanics puts a limit on the amount of information that can be gained by performing a measurement of an unknown state. This concept, arising from the fact that it is impossible to measure an unknown state without disturbing it, has been studied in the context of quantum state estimation [1][2][3]. Quantum state estimation is typically concerned with how to optimally measure and estimate a given quantum state. In some contexts it is desirable to limit the amount of backaction the quantum state experiences, and perform an optimal state estimation under this constraint. The other extreme in this continuum is the notion of weak measurements [4,5], where it is in principle possible to perform a measurement without disturbing the system at all, given a large number of copies [6]. This informationdisturbance tradeoff has been studied in a variety of different classes of quantum states such as single qubits [7], multiple copies of qubits [8,9] Figure 1). By measuring the phase shift via interference, the state of the BEC can be inferred. Because the PCI measurement does not destroy the atomic condensate, it can be applied repeatedly [21,22] nique is a useful resource for information readout in several proposed applications of ultra-cold atomic systems to metrology [23,24], quantum information and processing [25,26]. Other methods [27][28][29] also use a feedback mechanism to achieve greater control over the backaction induced by the measurement.In this paper we formulate a theory of PCI measurements at the single-shot level. We introduce a simple model that allows for the calculation of the backaction on the BEC, and the amount of information that is available by measurement of the light. Prior to this paper most works have modeled the effect of the backaction via continuous quantum measurement framework [30-

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Thermodynamics of Bose-Einstein-condensed clouds using phase-contrast imaging

Cited by 68 publications

References 17 publications

Macroscopic quantum information processing using spin coherent states

Macroscopic quantum information processing using spin coherent states

Collective excitation of a Bose-Einstein condensate by modulation of the atomic scattering length

Theory of Single-Shot Phase Contrast Imaging in Spinor Bose-Einstein Condensates

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