1,721,054 research outputs found
Probing the spacetime structure of vacuum entanglement
No full textWe introduce a framework for probing the spacetime structure of vacuum entanglement that exhibits infinite range correlations between the future and the past, as well as spatially separated regions. Our results are non-perturbative and analytical
Quantum state reduction via gravity, and possible tests using Bose-Einstein Condensates
No full textIt has been proposed that because of a fundamental conflict between basic principles of quantum mechanics and general relativity, a superposition between stationary quantum states that differ in mass distribution would reduce spontaneously to one or the other in a timescale inversely proportional to the gravitational self-energy of this mass-distribution difference. Here, we present arguments in favour of this proposal and suggest a possible test using Bose-Einstein condensates
Testing small scale gravitational wave detectors with dynamical mass distributions
No full textThe recent discovery of gravitational waves by the LIGO-Virgo collaboration created renewed interest in the investigation of alternative gravitational wave detector designs, such as small scale resonant detectors. In this article, it is shown how proposed small scale detectors can be tested by generating dynamical gravitational fields with appropriate distributions of moving masses. A series of interesting experiments will be possible with this setup. In particular, small scale detectors can be tested very early in the development phase and tests can be used to progress quickly in their development. This could contribute to the emerging field of gravitational wave astronomy
Active interferometry with gaussian channels
No full textWe consider an interferometer that contains active elements, such as a parametric amplifier, with general two-mode Gaussian unitary channels rather than the usually considered phase-shift channel. We concentrate on a scheme based on the recently proposed pumped-up SU(1,1) active interferometer where all input particles participate in the parameter estimation, and from which a conventional SU(1,1) interferometer is a limiting case. Using the covariance matrix formalism, we derive the quantum Fisher information of this active interferometer with a general two-mode Gaussian unitary channel, as well as the sensitivity for a number-sum measurement scheme, finding simple expressions for the latter. As an example application, we apply our results to Bose-Einstein condensates (BECs), and in particular a BEC gravitational-wave detector based on resonance, finding that the sensitivity of the detector can be improved by several orders of magnitude with this new interferometry scheme
On relativistic particle creation in Bose-Einstein condensates
No full textWe show that particle creation of Bogoliubov modes in a Bose-Einstein
condensate due to the accelerated motion of the trap is a genuinely
relativistic effect. To this end we show that Bogoliubov modes can be
described by a time rescaling of the Minkowski metric. A consequence of
this is that Rindler transformations are perceived by the phonons as
generalised Rindler transformations where the speed of light is replaced
by the speed of sound, enhancing particle creation at small velocities.
Since the non-relativistic limit of a Rindler transformation is just a
Galilean transformation entailing no length contraction or time
dilation, we show that the effect vanishes in the non-relativistic
limit
Observer-dependent entanglement
No full textUnderstanding the observer-dependent nature of quantum entanglement has been a central question in relativistic quantum information. In this paper, we will review key results on relativistic entanglement in flat and curved spacetime and discuss recent work which shows that motion and gravity have observable effects on entanglement between localized systems.</p
Quantum and classical effects in a light-clock falling in Schwarzschild geometry
No full textQuantum theory and relativity offer different conceptions of time. To explore the conflict between them, we study a quantum version of the light-clock commonly used to illustrate relativistic time dilation. This semiclassical model combines elements of both theories. We show for Gaussian states of the light field that the clock time is independent of the initial state. We calculate the discrepancy between two such clocks when one is held in a gravitational field and the other is left to fall a certain distance. Contrasting our results with the case of pointlike observers in general relativity, as well as classical light-clocks, we find both quantitative and qualitative differences. We find that the quantum contribution to the discrepancy between the two clocks increases with the gravitational field strength, and results in a minimum resolution of the dropped clock (distinct from the quantum uncertainty in its measurement)
Optimal probe states for the estimation of Gaussian unitary channels
No full textWe construct a practical method for finding optimal Gaussian probe states for the estimation of parameters encoded by Gaussian unitary channels. This method can be used for finding all optimal probe states, rather than focusing on the performance of specific states as shown in previous studies. As an example, we apply this method to find optimal probes for the channel that combines the phase-change and squeezing channels, and for generalized two-mode squeezing and mode-mixing channels. The method enables a comprehensive study of temperature effects in Gaussian parameter estimation. It has been shown that the precision in parameter estimation using single-mode states can be enhanced by increasing the temperature of the probe. We show that not only higher temperature, but also larger temperature differences between modes of a Gaussian probe state can enhance the estimation precision
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