Quantum interference

Xiangming Hu, Wang Fei

It has been predicted that a driven three-level V atom can emit strongly correlated fluorescence photons in the presence of quantum interference. Here we examine the effects of quantum interference on the intensity correlation of fluorescence photons emitted from a driven three-level Λ atom. Unexpectedly, strong correlation occurs without quantum interference. The quantum interference tends to reduce the correlation function to a normal level. The essential difference between these two cases is traced to the different effects of quantum interference on coherent population trapping (CPT). For the V atom, quantum interference and coherent excitation combine to lead to CPT. For the Λ atom, however, the quantum interference tends to spoil CPT while the coherent excitation induces the effect.

Ivars Peterson

David S. Simon

Partha Pratim Sahu

Complex multi-photon quantum interference states are indispensable requisites for integrated quantum optic processing and quantum communication technologies. Here, two mode interference (TMI) coupler has been presented to demonstrate HOM model of multi-photons (N > 2) Quantum interference. The experiment of three and four photons quantum interference have been performed and coincidence rate of three and four photons quantum interference have been measured and quantum visibilities are obtained as ~ 0.783 ± 0.009 and ~ 0.85 ± 0.009 respectively at 3 dB TMI coupling length of 11.5 μm. High fabrication tolerance of quantum fidelity of TMI coupler has been achieved due to having less number of design parameters in comparison to directional coupler and multimode interference coupler. Our results pave the way to achieve multi-photons quantum entanglement in compact device.

Bernard F. Burke

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.