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Register a new userClassical analogue of the Unruh effect
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In the Unruh effect an observer with constant acceleration perceives the quantum vacuum as thermal radiation. The Unruh effect has been believed to be a pure quantum phenomenon, but here we show theoretically how the effect arises from the classical correlation of noise. We demonstrate this idea with a simple experiment on water waves where we see the first indications of a Planck spectrum in the correlation energy.
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We study the estimation of parameters in a quantum metrology scheme based on entangled many-body Unruh-DeWitt detectors. It is found that the precision for the estimation of Unruh effect can be enhanced via initial state preparations and parameter selections. It is shown that the precision in the estimation of the Unruh temperature in terms of a many-body-probe metrology is always better than the precision in two probe strategies. The proper acceleration for Bobs detector and the interaction between the accelerated detector and the external field have significant influences on the precision for the Unruh effects estimation. In addition, the probe state prepared with more excited atoms in the initial state is found to perform better than less excited initial states. However, different from the estimation of the Unruh temperature, the estimation of the effective coupling parameter for the accelerated detector requires more total atoms but less excited atoms in the estimations.
We aim to build a simple model of a gas with temperature ($T$) in thermal equilibrium with a black-body that plays the role of the adiabatically expanding universe, so that each particle of such a gas mimics a kind of particle (quantum) of dark energy, which is inside a very small area of space so-called Planck area ($l_p^{2}$), that is the minimum area of the whole space-time represented by a huge spherical surface with area $4pi r_u^2$, $r_u$ being the Hubble radius. So we should realize that such spherical surface is the surface of the black-body for representing the universe, whose temperature ($T$) is related to an acceleration ($a$) of a proof particle that experiences the own black-body radiation according to the Unruh effect. Thus, by using this model, we derive the law of universal gravitation, which leads us to understand the anti-gravity in the cosmological scenario and also estimate the tiny order of magnitude of the cosmological constant in agreement with the observational data.
One of the primary reasons behind the difficulty in observing the Unruh effect is that for achievable acceleration scales the finite temperature effects are significant only for the low frequency modes of the field. Since the density of field modes falls for small frequencies in free space, the field modes which are relevant for the thermal effects would be less in number to make an observably significant effect. In this work, we investigate the response of a Unruh-DeWitt detector coupled to a massless scalar field which is confined in a long cylindrical cavity. The density of field modes inside such a cavity shows a {it resonance structure} i.e. it rises abruptly for some specific cavity configurations. We show that an accelerating detector inside the cavity exhibits a non-trivial excitation and de-excitation rates for {it small} accelerations around such resonance points. If the cavity parameters are adjusted to lie in a neighborhood of such resonance points, the (small) acceleration-induced emission rate can be made much larger than the already observable inertial emission rate. We comment on the possibilities of employing this detector-field-cavity system in the experimental realization of Unruh effect, and argue that the necessity of extremely high acceleration can be traded off in favor of precision in cavity manufacturing for realizing non-inertial field theoretic effects in laboratory settings.
We consider further on the problem of the analogue Hawking radiation. We propose a fourth order ordinary differential equation, which allows to discuss the problem of Hawking radiation in analogue gravity in a unified way, encompassing fluids and dielectric media. In a suitable approximation, involving weak dispersive effects, WKB solutions are obtained far from the horizon (turning point), and furthermore an equation governing the behaviour near the horizon is derived, and a complete set of analytical solutions is obtained also near the horizon. The subluminal case of the original fluid model introduced by Corley and Jacobson, the case of dielectric media are discussed. We show that in this approximation scheme there is a mode which is not directly involved in the pair-creation process. Thermality is verified and a framework for calculating the grey-body factor is provided.
We study the anti-Unruh effect for an entangled quantum state in reference to the counterintuitive cooling previously pointed out for an accelerated detector coupled to the vacuum. We show that quantum entanglement for an initially entangled (spacelike separated) bipartite state can be increased when either a detector attached to one particle is accelerated or both detectors attached to the two particles are in simultaneous accelerations. However, if the two particles (e.g., detectors for the bipartite system) are not initially entangled, entanglement cannot be created by the anti-Unruh effect. Thus, within certain parameter regime, this work shows that the anti-Unruh effect can be viewed as an amplification mechanism for quantum entanglement.
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