Creating and sharing knowledge for telecommunications

Approaches for Error Mitigation in Quantum Computing and Sensing

on 22-07-2019

... Stephen Gray, Argonne National Laboratory, Chicago, USA

Date & time: Monday, July 22nd, 15:00h
Location: Amphitheatre Ea3, North Tower, IST, Lisbon

Current digital or logic-gate-based quantum computers and, indeed, those that will emerge within the next few years or so have limited numbers (20-200) of noisy qubits. This period has been dubbed the “noisy intermediate-scale quantum” era or NISQ era. Since fault-tolerant error correction procedures involve many physical qubits representing each logical qubit, it is difficult or not possible to apply them to non-trivial algorithms running on NISQ era computers. It is possible, however, to develop error mitigation strategies that either do not
involve any extra qubits or perhaps just a limited number of extra ones. These approaches effectively replace the additional error-correcting qubits with additional runs of the quantum algorithm and extrapolation ideas. Such approaches also apply to estimates of quantum observables in general, including quantum sensing protocols such as Ramsey fringe measurements. Two such approaches developed by us are discussed.This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

Stephen Gray received a B.Sc. degree in chemistry from Carleton University, Ottawa, in 1977 and a Ph.D. degree in chemistry from UC Berkeley in 1982. After post-doctoral work at Oxford University (1982-84) and The University of Chicago (1984-86) he was an Assistant Professor in the Chemistry Department at Northern Illinois University before joining Argonne in 1990 as a staff scientist in the Chemistry Division. He moved on to become Group Leader of the Theory and Modeling Group at Argonne’s Center for Nanoscale Materials in 2009. More Information..

Light-matter entanglement over 50 km of optical fibre

on 16-07-2019

... Ben Lanyon, Institute for Quantum Optics and Quantum Information and the University of Innsbruck

Date & time: Tuesday, July 16th, 15:00h
Location: Sala de formação avançada, 2nd floor of the Physics Department building, IST

When shared between remote locations, entanglement opens up fundamentally new capabilities for science and technology. Envisioned quantum networks use light to distribute entanglement between their remote matter-based quantum nodes. In this short talk, I will present our observation of entanglement between matter (a trapped ion) and light (a photon) over 50 km of optical fibre [1]: two orders of magnitude further than the state of the art and a practical distance to start building large-scale quantum networks. Our methods include an efficient source of ion-photon entanglement via cavity-QED techniques (0.5 probability on-demand fibre-coupled photon from the ion) and a single photon quantum frequency converter to the 1550 nm telecom C band (0.25 fibre-coupled device efficiency). Modestly optimising and duplicating our system could allow for 100 km-spaced ion-ion entanglement at rates over 1 Hz. Our results therefore show a path to entangling remote registers of quantum-logic capable trapped-ion qubits, and the optical atomic clock transitions that they contain, spaced by hundreds of kilometres. More Information..