COIN — Coherence Observation by Interference Noise

Opher Kinrot

Yehiam Prior, Ilya Sh. Averbukh, Opher Kinrot

We present a novel approach — Coherence Observation by Interference Noise (COIN) — for the measurement of coherence. The method is based on analysis of the quantum interference fluctuations (noise) in the incoherent emission from a medium, following the excitation by a pair of time delayed pulses with random relative phase. In addition to spectroscopic applications, the new method is useful for the characterization of short pulses and their wavelength determination.

Vojtech Szőcs, Andreas Tortschanoff, Tibor Pálszegi +2 more

The technique of COIN (coherence observation by interference noise) relies on the measurement of correlated fluorescence fluctuations subsequent to two-pulse excitation with randomized relative phase [Kinrot et al., Phys. Rev. Lett. 75, 3822 (1995)]. In this paper, a comprehensive theoretical study on the use of random-phase fluorescence interferometry in the measurement of solid-state, molecular coherence is given. Optical response functions in terms of populations expanded to second order in a perturbational approach are presented for a guest/host system that are based on a generalized Bloch–Liouville formalism including inhomogeneous site broadening and harmonic vibrational modes. The theoretical treatment is intended to explain the coherence and coherence loss mechanisms measured, very recently, in the pentacene/p-terphenyl mixed crystal at low phonon temperatures. The expressions derived within the limits of the usual approximations are quite general and valid for both δ- and finite-width pulses. The perturbative solutions reproduce the temperature variation of the experimental COIN interferograms and reveal the effects of inhomogeneous dephasing and impurity–bath coupling, quite satisfactorily.

E. Wolf

Shivani Singh, C. M. Chandrashekar

Quantum walk has played an important role in development of quantum algorithms and protocols for quantum simulations. The speedup observed in quantum walk algorithms is attributed to quantum interference of spreading wave packet in position space. Similarly, localization in quantum walk due to disorder is also attributed to quantum interference effect. Therefore, it is intriguing to have a closer look and understand the way quantum interference manifests in different forms of quantum walk dynamics. Here we will use interference measure to quantify the interference in position space and coin space, together and independently. This interference measure helps us to differentiate localisation seen in quantum walks due to different forms of disorder and topological effects. We also shown that the interference measure in the coin space alone can serve as an indicator of the spatially localized quantum state. Comparing the result of interference and correlated coherence with the entanglement dynamics we show that all the intricate features of entanglement is captured by correlated coherence. This will give us a better understanding of role of quantum interference in quantum dynamics and its effect on entanglement. With the control over quantum walk dynamics and quantum interference, exploring the possibility of using interference as resource will be of immediate interest.

Z. Ficek, S. Swain, William T. Rhodes +9 more