Archive for Bell Inequality

Euclid Diversity Matters

Posted in Biographical, Euclid, Harassment Bullying etc with tags , , , , , on June 22, 2023 by telescoper

It was officially announced at the Euclid Consortium Meeting in Copenhagen this morning that I have been appointed to the role of Chair of the Euclid Consortium Diversity Committee (ECDC). This has been in the pipeline for a while, but I have refrained from saying anything publicly until the appointment was endorsed by the Euclid Consortium Lead (ECL) and Euclid Consortium Board (ECB) which has now happened.

The previous Chair, Prof. Mathilde Jauzac, is stepping down because her term on the ECDC has come to an end. I’ve been a member of the ECDC for three years during which time Mathilde has done a brilliant job as Chair and she’ll be a very difficult act to follow in this role. There was a standing ovation in the room this morning when Mathilde finished delivering her final ECDC report. It will be down to me to deliver next year’s report, at the 2024 Euclid Consortium Meeting, which will be in Rome.

Instead of trying to describe the role and activities of the ECDC generally, I will direct you to the information given on the brand new Euclid Consortium website which is a one-stop shop for everything to do with Euclid. You can find specific information about Equity, Diversity and Conduct there and/or on the ECDC’s own public website here from which I’ve taken a screengrab of the nice banner:

Just for information, the Euclid Consortium has about 2700 members so it really is a very large organization, and it is the aim of the ECDC to encourage a positive and inclusive environment within it for the benefit of everyone in it.

I’m looking forward to this role for the next year. I have only one year left of my term left on the ECDC so I will almost certainly be Chair for one year only. As regular readers of this blog – both of them – will know, I am on sabbatical next year which means I should have time to take on this responsibility, which I wouldn’t be able to do if I had my full teaching and admin load.

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A Very Clever Experimental Test of a Bell Inequality

Posted in The Universe and Stuff with tags , , on August 26, 2015 by telescoper

Travelling and very busy most of today so not much time to post. I did, however, however get time to peruse a very nice paper I saw on the arXiv with the following abstract:

For more than 80 years, the counterintuitive predictions of quantum theory have stimulated debate about the nature of reality. In his seminal work, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Bell showed that in any local realist theory the correlations between distant measurements satisfy an inequality and, moreover, that this inequality can be violated according to quantum theory. This provided a recipe for experimental tests of the fundamental principles underlying the laws of nature. In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we report on a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell’s inequality. We employ an event-ready scheme that enables the generation of high-fidelity entanglement between distant electron spins. Efficient spin readout avoids the fair sampling assumption (detection loophole), while the use of fast random basis selection and readout combined with a spatial separation of 1.3 km ensure the required locality conditions. We perform 245 trials testing the CHSH-Bell inequality S≤2 and find S=2.42±0.20. A null hypothesis test yields a probability of p=0.039 that a local-realist model for space-like separated sites produces data with a violation at least as large as observed, even when allowing for memory in the devices. This result rules out large classes of local realist theories, and paves the way for implementing device-independent quantum-secure communication and randomness certification.

While there’s nothing particularly surprising about the result – the nonlocality of quantum physics is pretty well established – this is a particularly neat experiment so I encourage you to read the paper!

Perhaps some day someone will carry out this, even neater, experiment!

PS Anyone know where I can apply to for a randomness certificate?

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