A novel experimental approach for the detection of the dynamical Casimir effect

Abstract

The Casimir effect is a well-known macroscopic consequence of quantum vacuum fluctuations, but whereas the static effect (Casimir force) has long been observed experimentally, the dynamic Casimir effect is up to now undetected. From an experimental viewpoint a possible detection would imply the vibration of a mirror at gigahertz frequencies. Mechanical motions at such frequencies turn out to be technically unfeasible. Here we present a different experimental scheme where mechanical motions are avoided, and the results of laboratory tests showing that the scheme is practically feasible. We think that at present this approach gives the only possibility of detecting this phenomenon. PACS numbers: 12.20.Fv, 42.50.Dv, For any quantum field, the vacuum is defined as its ground state. Differently than in the classic case, this ground state, due to the uncertainty principle, is not empty, but filled with field fluctuations around a zero mean value. Moreover this vacuum state depends on the field boundary conditions : if they change, there will be a correspondingly different vacuum (whose fluctuations will have a different wavelength spectrum). Thus a quantum vacuum state may be equivalent to real particles of a new vacuum after a change in boundary conditions.If we consider the electromagnetic field, the peculiar nature of the quantum vacuum has experimentally observable consequences in the realm of microscopic physics, such as natural widths of spectral lines, Lamb shift, anomalous magnetic moment of the electron and many more. It is perhaps even more striking that there exist also observable effects at a macroscopic level. The Casimir force (static Casimir effect [1,2]) is one of these macroscopic effects which has been observed experimentally. A dynamic Casimir effect is also predicted to occur when one boundary is accelerated in a nonuniform way, as for instance when a metal surface undergoes harmonic oscillations. In this case a number of virtual photons from the vacuum are converted into real photons ("Casimir radiation"), while the moving metal surface loses energy [3,4,5].It is worth notice that, whereas the static Casimir effect has been observed by several experiments [6], the Casimir radiation is to date unobserved, in spite of the abundant theoretical work done in this field [7,8,9,10,11] (see [8] for a historical review and a bibliography of the relevant studies). We argue that this lack of experimental activity stems from the rooted idea of using mechanical oscillations. We shall show that this is unfeasible with present-day techniques.Here we shall present a new experimental approach where an effective motion is generated by the excitation of a plasma in a semiconductor. In terms of power this effective motion is much more convenient than a mechanical motion, since in a metal mirror only the conduction electrons reflect the electromagnetic waves, whereas a great amount of power would be wasted in the acceleration of the much heavier nuclei. Some authors [12,13,14] have made use of our idea in order to cons...

Dynamical Casimir effect in stochastic systems: Photon harvesting through noise

“…To date, several experimental schemes to observe the DCE have been proposed [12][13][14][15][16][17][18], but only a few have succeeded [19,20]. The main limitation is because a non-negligible photon production can only be attained when the mirror's speed becomes comparable to the speed of light.…”

The Heisenberg-Langevin model of a quantum damped harmonic oscillator with time-dependent frequency and damping coefficients

“…If the interaction between the modes can be neglected, then it seems reasonable to believe that one can use the model of quantum time-dependent oscillator to evaluate the number of photons created in the selected mode [11,12]. The most promising scheme of obtaining the required changes of the cavity parameters consists in the periodical creation of a thin highly conducting layer on the surface of a semiconductor slab (attached to one of the cavity walls) by means of short (picosecond) laser pulses [13]. However, dealing with the semiconductor mirror one cannot neglect the fact that the dielectric permeability (x) of the conducting medium (semiconductor slab after excitation by the laser pulse) is a complex function…”

Prospects of employing superconducting stripline resonators for studying the dynamical Casimir effect experimentally

“…Achieving the condition ξQ > 1 requires that the shift in the resonance frequency exceeds the width of its peak. So far the DCE has not been verified experimentally [9,10]. It turns out that creation of photons in the case of a cavity with moving walls requires that the peak velocity of the moving walls must be made comparable to light velocity, a task which is extremely difficult experimentally [11].…”

“…The modulation frequency achieved by this method is limited by the recombination time of electron-hole pairs, which can be relatively fast in some semiconductors [13]. Based on these ideas, a novel experimental approach for the detection of the DCE was recently proposed [9]. However, implementing this approach might be very difficult [14].…”

“…The frequency offset ∆f = 800 Hz is chosen to be much smaller than the resonance width f 0 /Q. Note that the laser power is approximately eight orders of magnitude lower than the power used in the experimental approach proposed by Braggio et al [9]. Fig.…”