Enhanced Dynamic Casimir Effect in Temporally and Spatially Modulated Josephson Transmission Line

Abstract

Real photon pairs can be created in a dynamic cavity with an oscillating boundary or temporally modulated refractive index of the constituent medium. This effect is called dynamic Casimir effect (DCE), which represents one of the most amazing predictions of quantum field theory. The DCE has been experimentally observed in Josephson metamaterials embedded in a microwave cavity. However, the efficiency of the observed DCE is extremely weak, entailing a complex external signal enhancement process to detect the signal. Here, it is shown that the DCE can be drastically enhanced in a dynamic 1D cavity consisting of a superconducting quantum interference device (SQUID)‐based Josephson transmission line with both temporal and spatial modulation on the effective inductance profile through flux‐biasing. Such a system can resonantly generate photons at driving frequencies equal to even or odd integer times of that of the fundamental cavity mode governed by the symmetry of the spatial modulation. Interesting spectral and scaling behaviors for photons excited at the band edge are further observed. The discovery introduces a new degree of freedom—spatial modulation—to enhance the efficiency of DCE.

Fifty Years of the Dynamical Casimir Effect

“…This arrangement can be considered as a one-dimensional system with periodically varying distributed parameters. The results of that experiments stimulated many theoretical papers, suggesting further improvements of the experimental schemes [324][325][326][327][328][329][330][331][332][333][334][335][336][337]. The circuit QED with "artificial atoms" (qubits) was the subject of studies [338][339][340][341][342][343][344][345][346][347][348][349][350].…”

Generation of photons from vacuum in cavity via time-modulation of a qubit invisible to the field

“…In this case, one can view the atom as a microscopic constituent of the intracavity medium that shifts its effective frequency; moreover, such scheme benefits from leaving the Fock states of the cavity field time-independent (as opposed to the standard case of time-varying cavity frequency, when the annihilation operator and the Fock states depend explicitly on time [9]). These nonstationary circuit QED setups exhibit several important phenomena beside photon generation from vacuum, e. g.: generation of atom-field entangled states and novel nonclassical states of light [38,39], quantum simulation [40][41][42], implementation of quantum gates [43], engineering of effective interactions [44], implementation of quantum thermal engines [45,46], photon generation and atom-field effective coupling via multiphoton transitions [47,48], anti-dynamical Casimir effect (coherent annihilation of excitations due to external modulation) [49][50][51][52], photon generation by both temporal and spatial modulation in metamaterials [53], vacuum Casimir-Rabi oscillations in optomechanical systems [54], etc [5].…”

Single Gyrotropic Particle as a Heat Engine

“…The study of equilibrium and nonequilibrium Casimir forces − has been of fundamental importance since such studies illustrate some of the surprising consequences that quantum and thermal fluctuations can generate in nanoscale systems. − Moreover, there are emerging interests in seeking to control these forces, such as through dynamic modulation, or to design these forces to achieve specific functionalities, such as to achieve stable mechanical equilibrium. − …”