The concept of quantum entanglement has been a key driving force of the Quantum Information Science (QIS) revolution. Entangled particles display correlations that are stronger than anything allowed by classical physics, and can serve as a powerful resource for quantum-enhanced technologies. Although entanglement has now been observed in a number of different physical systems—including electrons, atoms, and photons—significant advances in the production and control of entangled particles are crucial for the advancement of experimental QIS. Entangled photons, for example, possess a variety of desirable properties that may enable applications in quantum communications, quantum sensing, and quantum computing. However, the most widely used and high-quality source of entangled photons is based on an inherently random process that only rarely emits photon pairs. This project aims to overcome this randomness and develop a true “push-button†source of entangled photon pairs on demand. The realization of such a source will advance current entanglement-based photonic QIS experiments from “proof-of-principle†laboratory demonstrations towards practical real-world QIS applications. At the same time, investigations of the fundamental physics behind this on-demand source will serve the national interest of progressing our current understanding of quantum science. The project also provides education and research experience for both graduate and undergraduate students. This represents an outstanding opportunity for training the next generation of QIS scientists.
The approach is based on the use of Parametric Down Conversion (PDC)—a process that is known to produce high-quality entangled photon pairs, but in a completely random fashion. The core idea is to overcome this inherent randomness by combining several random PDC pairs into one useful pair using techniques from the Linear Optics Quantum Computing (LOQC) paradigm, coupled with robust Cyclical Quantum Memory (CQM) devices. Roughly speaking, destructive LOQC-type measurements performed on a subset of the emitted photons are used to probabilistically “herald†the presence of exactly one remaining pair. The heralded pair is then actively switched into two loop-based CQM devices, which safely store the photons while maintaining their entanglement. The entangled pair can then be released on-demand when needed (ie. “push-button†operation). The experimental methods to be employed involve the use of synchronized ultrafast pulsed PDC sources, heralding signals based on quantum interference effects and single-photon detection, and high-speed electro-optic-based switching and storage loops. In many ways, this source of entangled photon pairs on-demand can be viewed as a small-scale special-purpose LOQC device with numerous practical applications in QIS.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
