arXiv subjects

V. Gopal

Publications and source records attributed to V. Gopal.

4 recordsLinked to original sources

arXiv2007

Ultrahigh Precision Absolute and Relative Rotation Sensing using Fast and Slow Light

We describe a resonator based optical gyroscope whose sensitivity for measuring absolute rotation is enhanced via use of the anomalous dispersion characteristic of superluminal light propagation. The enhancement is given by the inverse of the group index, saturating to a bound determined by the group velocity dispersion. We also show how the offsetting effect of the concomitant broadening of the resonator linewidth may be circumvented by using an active cavity. For realistic conditions, the enhancement factor is as high as 106. We also show how normal dispersion used for slow light can enhance relative rotation sensing in a specially designed Sagnac interferometer, with the enhancement given by the slowing factor

quant-ph↗

arXiv2006

Light-Shift Imbalance Induced Blockade of Collective Excitations Beyond the Lowest Order

Current proposals focusing on neutral atoms for quantum computing are mostly based on using single atoms as quantum bits (qubits), while using cavity induced coupling or dipole-dipole interaction for two-qubit operations. An alternative approach is to use atomic ensembles as qubits. However, when an atomic ensemble is excited, by a laser beam matched to a two-level transition (or a Raman transition) for example, it leads to a cascade of many states as more and more photons are absorbed^1. In order to make use of an ensemble as a qubit, it is necessary to disrupt this cascade, and restrict the excitation to the absorption (and emission) of a single photon only. Here, we show how this can be achieved by using a new type of blockade mechanism, based on the light-shift imbalance (LSI) in a Raman transition. We describe first a simple example illustrating the concept of light shift imbalanced induced blockade (LSIIB) using a multi-level structure in a single atom, and show verifications of the analytic prediction using numerical simulations. We then extend this model to show how a blockade can be realized by using LSI in the excitation of an ensemble. Specifically, we show how the LSIIB process enables one to treat the ensemble as a two level atom that undergoes fully deterministic Rabi oscillations between two collective quantum states, while suppressing excitations of higher order collective states.

quant-ph↗

arXiv2005

Enhancement of interferometric precision using fast light

We show that anomalous dispersion characteristic of fast-light can be used to enhance the sensitivity of optical interferometry under certain conditions. In particular, we show that a dual-chamber Fabry-Perot interferometer with a shared mirror-pair can be used in a way so that its sensitivity is increased by operating near the critically anomalous dispersion condition where the group index is much less than unity. The enhancement factor can be as high as 108 for realistic conditions. The process of bi-frequency pumped Raman gain in a lambda-type atomic medium can be used to achieve this effect.

quant-ph↗

arXiv2003

Wavelength Teleportation via Distant Quantum Entanglement

Recently, we have shown theoretically [1] as well as experimentally [2] how the phase of an electromagnetic field can be determined by measuring the population of either of the two states of a two-level atomic system excited by this field, via the so-called Bloch-Siegert oscillation resulting from the interference between the co- and counter-rotating excitations. Here, we show how a degenerate entanglement, created without transmitting any timing signal, can be used to teleport this phase information. This phase-teleportation process may be applied to achieve wavelength teleportation, which in turn may be used for frequency-locking of remote oscillators.

quant-ph↗