Suroj Dey joined us from IISER Mohali for a PhD. He will be working at the interface of quantum mechanics and gravity.

New paper published in the IOP journal Classical and Quantum Gravity.

We present an accreditation protocol for analogue, i.e., continuous-time, quantum simulators.

Matt Christensen has joined the Quantum Information Group within the HetSys CDT.

Ellen's team recently came 2nd in the National Quantum Computing Centre Hackathon

A new paper on quantum information-theoretic formulation of electric dipole estimation in quantum spectroscopy of two-level systems is the Physical Review A Editor's suggestion.

Greg's research interests are in computational complexity theory, including quantum complexity.

Andrew, Theo, and Animesh's paper, Partition-function estimation: Quantum and quantum-inspired algorithms, has been published in PRA.

Ellen Devereux from Fujitsu and Sourav Das from the Indian Institute of Science Education and Research, Mohali join us for their PhDs.

Sam's work on accreditation of quantum computations on IBM's hardware published.

Aaron Malcolm joins us from the University of St. Andrews his PhD. Will Hughes and Gongyu Ni join us for their Masters from Cardiff University Jilin University respectively.

Sharmila Balamurugan joins us from the Indian Institute of Technology, Madras, India, and Francesco Albarelli (re)joins us from the University of Warsaw, Poland.

Our paper on a signature of the quantum nature of gravity in the quantum mechanical squeezing of the differential motion of two identical masses has been published.

Congratulations to Sam for winning the 2020 Faculty of Science and Department of Physics Thesis Prize!

What happens at the molecular lever when a photon hits the eye or light shines on a leaf?

Physical processes occurring on nanometre length scales and femtosecond time scales typically undergo complex dynamics involving multilevel quantum systems. Understanding such complex quantum dynamics is a major open challenge. Foremost among them is the dimension of the Hilbert space  involved, which determines the number of parameters necessary for understanding the dynamics. This is typically done by fitting models of various degrees of sophistication to experimental data.

In a work appearing on the cover of Physical Review Letters, volume 125, issue 8, we with collaborators at the University of Nanjing, China and the University of Ottawa, Canada, have shown that even noisy and saturating detectors can approach shot-noise-limited detection if used judiciously. Shot-noise-limited optical detection is the first, and often the most challenging, step to quantum-enhanced optical sensing. This work uses a technique called weak-value amplification and enables, over a range of input light intensity well beyond the dynamic range of the photodetector, shot-noise-limited detection. Weak-value amplification relies on the principle that only a subset of the photons contains almost all of the information about the sensed object.

As the first generation of quantum computers are now reaching the point where they can answer such otherwise impossible questions, it is necessary to consider how the answers of these early devices can be confirmed correct. The full power of quantum computing includes a wide range of problems for which this is not possible, instead demanding new techniques to test quantum computers. A new test has now been proposed by Samuele, Theodoros, and Animesh which can be used to make sure the quantum computer is working correctly without using excessive additional resources while still testing the entire quantum computer. Published in the New Journal of Physics (DOI:10.1088/1367-2630/ab4fd6), this protocol uses circuits which have the same form as the desired circuit but are formulated to give known outcomes. Based on the accuracy of these circuits they are able to place a statistical bound on how close the distribution the quantum computer gives is to the correct distribution.

Francesco, Jamie, and Animesh have published new work in Physical Review Letters which demonstrates that the Holevo Cramér-Rao bound, the fundamental limit to how precise any sensor can be, can be evaluated by numerically efficient methods. Computation of the Holevo Cramér-Rao bound requires the solving of a non-linear optimisation problem. In this publication Francesco, Jamie, and Animesh demonstrate that the necessary optimisation can be expressed as a convex optimisation problem. This realisation allows efficient numerical evaluation of the Holevo Cramér-Rao bound, opening up the possibility of practically applying it in quantum sensing problems.