Interference (wave propagation)

About: Interference (wave propagation) is a research topic. Over the lifetime, 26086 publications have been published within this topic receiving 321110 citations.

Quantum interference and correlation control of frequency-bin qubits

Abstract: Frequency-bin quantum information encoding offers an intriguing synergy with classical optical networks, with the ability to support many qubits in a single fiber. Yet, coherent quantum frequency operations prove extremely challenging due to the difficulties in mixing frequencies arbitrarily and with low noise. In this paper, we address such challenges and implement distinct quantum gates in parallel on two entangled frequency-bin qubits in the same optical fiber. Our basic quantum operation controls the spectral overlap between adjacent spectral bins, allowing us to observe frequency-bin Hong–Ou–Mandel interference with a visibility of 0.971±0.007. By integrating this tunability with frequency parallelization, we synthesize independent gates on entangled qubits and flip their spectral correlations, allowing us to observe strong violation of the separability bound. Our realization of closed, user-defined gates on frequency-bin qubits in parallel should find application in the development of fiber-compatible quantum information processing and quantum networks.

Theory of two-photon interference

Abstract: The interference effects that can be observed in the two output arms of a lossless beam splitter are calculated for incident light in the form of a photon-pair excitation in the two input arms. The output state that occurs when the photon pair is excited in a single input arm resembles that expected for independent classical particles, whereas quantum interference effects occur when the photon pair is divided between the two input arms. Detailed output photocount correlation functions are calculated for two-photon input states produced by a two-atom light source, a degenerate or nondegenerate parametric oscillator in a high-Q cavity, and an atomic cascade emission light source.

Tunable quantum interference in a 3D integrated circuit

Abstract: Integrated photonics promises solutions to questions of stability, complexity, and size in quantum optics. Advances in tunable and non-planar integrated platforms, such as laser-inscribed photonics, continue to bring the realisation of quantum advantages in computation and metrology ever closer, perhaps most easily seen in multi-path interferometry. Here we demonstrate control of two-photon interference in a chip-scale 3D multi-path interferometer, showing a reduced periodicity and enhanced visibility compared to single photon measurements. Observed non-classical visibilities are widely tunable, and explained well by theoretical predictions based on classical measurements. With these predictions we extract Fisher information approaching a theoretical maximum. Our results open a path to quantum enhanced phase measurements.

Entanglement, dephasing, and phase recovery via cross-correlation measurements of electrons.

Abstract: Determination of the path taken by a quantum particle leads to a suppression of interference and to a classical behavior. We employ here a quantum "which path" detector to perform accurate path determination in a two-path Mach-Zehnder electron interferometer, leading to full suppression of the interference. Following the dephasing process we recover the interference by measuring the cross correlation between the interferometer and detector currents. Under our measurement conditions every interfering electron is dephased by approximately a single electron in the detector-leading to mutual entanglement of approximately single pairs of electrons.

Joint transmission in indoor visible light communication downlink cellular networks

Abstract: In future visible light communication (VLC) systems, networked multi-cell operation is required to achieve seamless coverage and high data rate in typical indoor environments. We refer to this type of cellular network as optical atto-cell network. In such network, co-channel interference (CCI) between adjacent optical atto-cells limits the performance of the network. In order to maximise system throughput and improve signal quality in the whole coverage area, it is necessary to mitigate CCI. In this paper, the concept of multi-point joint transmission (JT) is adapted to a VLC cellular network. It can generally be described as concurrent data transmission from multiple cooperating base stations (BSs) to a mobile station (MS). In a VLC JT system, strong CCI is avoided by co-ordinated transmission and, in addition, we exploit a particular characteristic of intensity modulation (IM) systems. This is that signals always superimpose constructively which is in stark contrast to radio frequency (RF)-based systems. Therefore, the cell-edge user signal to interference plus noise ratios (SINRs) can be improved. The results show that the JT scheme improves the median SINR by 16.4 dB compared to a full frequency reuse system. Additionally, a JT system exhibits a 67.6% improvement in terms of median system throughput compared to a static resource partitioning system with a reuse factor of 3.