Using Quantum Mechanical Devices and Recent Developments

Arash Rahimi‐Iman

Craig Callender, Robert Weingard

Philosophers of science have not paid much attention to recent developments in quantum cosmology. This fact is surprising, since quantum cosmology is replete with conceptual issues involving (e.g.) the fundamental nature of time and space, the interpretation of quantum mechanics, and the ultimate meaning of probability. One notable exception, Quentin Smith, has recently examined the Hartle-Hawking (1983) proposal. Trying to make sense of the view, he resorts to an instrumentalist picture, which treats the proposal as merely a heuristic device for the algorithm responsible for predictions. While we do not examine Smith's account here, we would like to contrast it with the model presented in this note, in which a fully realistic interpretation of quantum cosmology is developed. Recently there has been a resurgence of interest in the de Broglie-Bohm causal interpretation of quantum mechanics.

Adeline Orieux, Marijn A. M. Versteegh, Klaus D. Jöns +1 more

Entanglement is one of the most fascinating properties of quantum mechanical systems; when two particles are entangled the measurement of the properties of one of the two allows the properties of the other to be instantaneously known, whatever the distance separating them. In parallel with fundamental research on the foundations of quantum mechanics performed on complex experimental set-ups, we assist today with bourgeoning of quantum information technologies bound to exploit entanglement for a large variety of applications such as secure communications, metrology and computation. Among the different physical systems under investigation, those involving photonic components are likely to play a central role and in this context semiconductor materials exhibit a huge potential in terms of integration of several quantum components in miniature chips. In this article we review the recent progress in the development of semiconductor devices emitting entangled photons. We will present the physical processes allowing the generation of entanglement and the tools to characterize it; we will give an overview of major recent results of the last few years and highlight perspectives for future developments.

Kyle DeBry

Superconducting single-photon detectors can detect photons from the UV to the infrared with quantum efficiencies above 90% and greater than MHz count rates. They consist of narrow, thin wires of superconductor biased near their critical current. When these wires absorb a photon, part of the wire stops superconducting and becomes resistive. This transition and sudden jump in resistance is what enables the detection of the photon. Over the past two decades, these devices have matured greatly as a technology and have found many applications ranging from quantum optics to astronomy. However, there are still multiple theories of the dominant mechanism behind these devices. Recently proposed theories suggest a more complicated but potentially more powerful detection mechanism, and experiments are only recently starting to demonstrate this effect and its potential applications. In this research, the capability to fabricate these intricate devices was developed. This requires high-quality deposition of the superconductors, precise machining of the devices with electron beam lithography, and accurate etching of the films. Many parts of the process have been characterized. Additionally, two new directions are being explored. The first attempts to exploit the recently proposed detection mechanism to make detectors with much wider wires, leading to faster detection rates. The second is the fabrication of superconducting single-photon detectors directly onto optical fibers, eliminating the need for complicated coupling structures and alignment of the detector with the fiber.

D K Roy