30 January 2018 Vlatko Vedral


Speaker             : Vlatko Vedral, University of Oxford
Title                     : An entanglement-based test of quantum gravity
Date                     : January 30, 2018 Tuesday
Time                    : 15:00
Cookie & Tea  : SCI 103 14:45
Place                   : SCI 103
web                       https://physics-seminars.ku.edu.tr

Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles. Most physicists, though, think it applies to everything, no matter what the size. The reason its distinctive features tend to be hidden is not always a simple matter of scale. Over the past few years experimentalists have seen quantum effects in a growing number of macroscopic systems. The quintessential quantum effect, entanglement, can even occur in large systems as well as warm ones – including living organisms – even though molecular jiggling might be expected to disrupt entanglement. Gravity, however, seems different and all existing quantum gravity proposals share the same problem. Their predictions are extremely hard to test in practice. Quantum effects in the gravitational field are exceptionally small, unlike those in the electromagnetic field. The fundamental reason, as I intend to elaborate on, is that the gravitational coupling constant is about 43 orders of magnitude smaller than the fine structure constant, which governs light-matter interactions. In that sense, the detection of gravitons – the hypothetical quanta of energy of the gravitational field predicted by certain quantum-gravity proposals – is deemed to be practically impossible.

In my talk I will present a different, quantum-information-theoretic approach, which circumvents the problem that quantum gravity is hard to test. I will discuss an experiment to witness quantum-like features in the gravitational field, by probing it with two masses each in a superposition of two locations. I will then argue that the degree of entanglement between the masses is an indirect witness of the quantisation of the field mediating the interaction. Remarkably, this experiment does not require any quantum control over gravity itself. It also seems possible to realise using the existing quantum technology.

Short Bio: Vlatko Vedral studied undergraduate theoretical physics at Imperial College London, where he also received a PhD for his work on “Quantum Information Theory of Entanglement” in 1998. He then was elected Elsag-Bailey post-doctoral research fellow in Oxford. He then held a research fellowship at Merton College Oxford before returning to Imperial College as the Governor’s lecturer to start a quantum information science research group, a position he held from 2000-2004. Before returning to Oxford, he was Centenary Professor of Quantum Information Science at Leeds University 2004-2009. Throughout his career he also held a number of visiting professorships in Vienna, Singapore (NUS) and at Perimeter Institute in Canada. He is currently a Professor of Quantum Information Science at the University of Oxford and Centre for Quantum Technologies at the National University of Singapore and a Fellow of Wolfson College. He has published more than 280 research papers in quantum mechanics and quantum information. He has written several textbooks and popular science books. He has written for popular science journals and major daily newspapers, as well as doing extensive radio programmes and television interviews.