Matthew's posts

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Public

I am a bit late on the shameless self promotion, but if this paper is right I could always .... ah, forget it, retrocausality jokes suck.

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The pedant in me will note that Musser did not quite get at the key feature of the experiment that Spekkens' proposed, which is that you can get no information about the parity of the two bits. What he has described is a 2->1 random access code, which is a bit different. Otherwise, an interesting article about an under-reported topic: https://www.quantamagazine.org/20160119-time-entanglement/

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https://journals.aps.org/pra/edannounce/10.1103/PhysRevA.93.010001 Suggestion: "and quantum foundations".

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Please comment on the original post to reserve a seat.

The first Q+ Hangout of the year is on the 26th of January!

As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment. We also encourage individuals interested in active participation---which typically involves asking questions after the talk---to join the hangout. Otherwise you can watch on the livestream. Details follow.

Title: Toward physical realizations of information-theory models for small-scale thermodynamics

Speaker: Nicole Yunger Halpern (Caltech, Institute for Quantum Information and Matter)

Abstract: Small scales are increasingly controllable in experiments and technologies. Such settings involve statistical mechanical concepts, such as work, heat, and entropy. Heat dissipation threatens miniaturized transistors, and the work required to stretch single DNA molecules has been measured. Yet statistical mechanics describes large systems. Two mathematical toolkits developed in quantum information theory marry statistical mechanics with small scales. Thermodynamic resource theories and one-shot information theory have exploded in popularity recently. The time is ripe to realize their potential with real physical systems. I will explain why while introducing these toolkits. I will discuss which aspects of them need realizing and via what steps we can shift them toward experiments.

Reference: http://arxiv.org/abs/1509.03873

As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment. We also encourage individuals interested in active participation---which typically involves asking questions after the talk---to join the hangout. Otherwise you can watch on the livestream. Details follow.

Title: Toward physical realizations of information-theory models for small-scale thermodynamics

Speaker: Nicole Yunger Halpern (Caltech, Institute for Quantum Information and Matter)

Abstract: Small scales are increasingly controllable in experiments and technologies. Such settings involve statistical mechanical concepts, such as work, heat, and entropy. Heat dissipation threatens miniaturized transistors, and the work required to stretch single DNA molecules has been measured. Yet statistical mechanics describes large systems. Two mathematical toolkits developed in quantum information theory marry statistical mechanics with small scales. Thermodynamic resource theories and one-shot information theory have exploded in popularity recently. The time is ripe to realize their potential with real physical systems. I will explain why while introducing these toolkits. I will discuss which aspects of them need realizing and via what steps we can shift them toward experiments.

Reference: http://arxiv.org/abs/1509.03873

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The next Q+ Hangout is on the 10th of December!

As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment. We also encourage individuals interested in active participation---which typically involves asking questions after the talk---to join the hangout. Otherwise you can watch on the livestream. Details follow.

Speaker: Antonio Acin, ICFO Barcelona

Title: Randomness certification in quantum and general non-signalling theories

Abstract: The non-local correlations observed among entangled quantum particles can be used to certify the presence of randomness in a device-independent way. We first introduce the main concepts and tools in this scenario. We then overview some of our recent results connecting certified randomness and non-locality. In particular, we (i) give quantum setups allowing for maximal randomness certification, that is, the outcomes obtained when measuring N devices define N random bits; (ii) prove that maximal randomness certification is impossible in general non-signalling theories; (iii) provide schemes to attain optimal randomness certification from two-qubit entangled states using general (non-projective) measurements; and (iv) show that an unbounded amount of randomness can be certified in a device-independent way using sequence of measurements.

As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment. We also encourage individuals interested in active participation---which typically involves asking questions after the talk---to join the hangout. Otherwise you can watch on the livestream. Details follow.

Speaker: Antonio Acin, ICFO Barcelona

Title: Randomness certification in quantum and general non-signalling theories

Abstract: The non-local correlations observed among entangled quantum particles can be used to certify the presence of randomness in a device-independent way. We first introduce the main concepts and tools in this scenario. We then overview some of our recent results connecting certified randomness and non-locality. In particular, we (i) give quantum setups allowing for maximal randomness certification, that is, the outcomes obtained when measuring N devices define N random bits; (ii) prove that maximal randomness certification is impossible in general non-signalling theories; (iii) provide schemes to attain optimal randomness certification from two-qubit entangled states using general (non-projective) measurements; and (iv) show that an unbounded amount of randomness can be certified in a device-independent way using sequence of measurements.

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Second article on the loophole free Bell test, by Andrew Grant, is now up: https://www.sciencenews.org/article/new-experiment-verifies-quantum-spookiness (behind a paywall unfortunately). In it, I only get quoted as saying that the bandwidth of the experiment is way to low to use it for practical device independent cryptography, which is perhaps a good counterweight to my Nobel superlatives in Zeeya's article.

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I was interviewed three times about the loophole free Bell test today. The first article, by Zeeya Merali, is up on Nature News: http://www.nature.com/news/quantum-spookiness-passes-toughest-test-yet-1.18255?WT.mc_id=TWT_NatureNews I am in good company, as the other interviewees are Anton Zeilinger and Nicholas Gisin. I figure I can keep up with such heavy hitters by saying that the work might win the Nobel prize.

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Loophole free Bell experiment

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I'm on the FQXi podcast again, this time with the audio from the panel discussion I took part in about communicating physics to the public. I previously blogged about my comments here: http://mattleifer.info/2015/05/05/on-outreach-and-education-for-the-foundations-of-physics/

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Sharing this more for the surprise that Andris Ambainis is apparently working on quantum foundations than for the result: http://arxiv.org/abs/1506.05174

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