Bell violation using entangled photons without the fair-sampling assumption

Giustina, Marissa; Mech, Alexandra; Ramelow, Sven; Wittmann, Bernhard; Kofler, Johannes; Beyer, J.; Lita, Adriana E.; Calkins, Brice; Gerrits, Thomas; Nam, Sae Woo; Ursin, Rupert; Zeilinger, Anton

doi:10.1038/nature12012

Cited by 517 publications

(616 citation statements)

References 34 publications

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“…Shocking as it may be, our world is not of this kind. Statistical inequalities, such as e = 1/4, derived on the assumption that the values of unmeasured physical quantities do exist and commonly referred to as Bell's inequalities 33 , have been violated in a number of painstaking experiments 33,34,35,36,37,38,39,40,41,42,43,44 . We shall not dwell on the philosophical implications of this experimental fact (volumes have been written on the subject), but simply point out that it should be embraced by all those who worry about secrecy because what does not exist cannot be eavesdropped, and so it is much easier to keep secrets in a non-classical world.…”

Section: Less Reality More Securitymentioning

confidence: 99%

The ultimate physical limits of privacy

Ekert

Renner

2014

Nature

127

104

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Among those who make a living from the science of secrecy, worry and paranoia are just signs of professionalism. Can we protect our secrets against those who wield superior technological powers? Can we trust those who provide us with tools for protection? Can we even trust ourselves, our own freedom of choice? Recent developments in quantum cryptography show that some of these questions can be addressed and discussed in precise and operational terms, suggesting that privacy is indeed possible under surprisingly weak assumptions.Edgar Allan Poe, an American writer and an amateur cryptographer, once wrote "… it may be roundly asserted that human ingenuity cannot concoct a cipher which human ingenuity cannot resolve …" 1 . Is it true? Are we doomed to be deprived of our privacy, no matter how hard we try to retain it? If the history of secret communication is of any guidance here, the answer is a resounding 'yes'. There is hardly a shortage of examples illustrating how the most brilliant efforts of code-makers were matched by the ingenuity of code-breakers 2 . Even today, the best that modern cryptography can offer are security reductions, telling us, for example, that breaking RSA, one of the most widely used public key cryptographic systems, is at least as hard as factoring large integers 3 . But is factoring really hard? Not with quantum technology. Indeed, RSA, and many other public key cryptosystems, will become insecure once a quantum computer is built 4 . Admittedly, that day is probably decades away, but can anyone prove, or give any reliable assurance, that it is? Confidence in the slowness of technological progress is all that the security of our best ciphers now rests on.This said, the requirements for perfectly secure communication are well understood. When technical buzzwords are stripped away, all we need to construct a perfect cipher is shared private randomness, more precisely, a sequence of random bits known as a 'cryptographic key'. Any two parties who share the key, we call them Alice and Bob (not their real names, of course), can then use it to communicate secretly, using a simple encryption method known as the one-time pad 5 . The key is turned into a meaningful message by one party telling the other, in public, which bits of the key should be flipped. An eavesdropper, Eve, who has monitored the public communication and knows the general method of encryption but not the key will not be able to infer anything useful about the message. It is vital though that the key bits be truly random, never reused, and securely delivered to Alice and Bob, who may be miles apart. This is not easy, but it can be done, and one can only be amazed how well quantum physics lends itself to the task of key distribution.Quantum key distribution, proposed independently by Bennett and Brassard 6 and by Ekert 7 , derives its security either from the Heisenberg uncertainty principle (certain pairs of physical properties are complementary in the sense that knowing one property necessarily precludes knowledge about the othe...

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Section: Less Reality More Securitymentioning

confidence: 99%

The ultimate physical limits of privacy

Ekert

Renner

2014

Nature

127

104

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“…If we denote by R the frequency of trials and by J the experimentally expected value, then, assuming small bias, the condition Z (N) (31) is likely to be reached after a run time of c 2 R (J− AB ) 2 . In a photonic Bell experiment with total collection efficiency η ≈ 75 % [31,32], one downconversion pair in 10 3 pulses, and reasonable state visibility and rate of dark/background counts, the CH-E value would be of the order of J ∼ 10 −6 . (The low probability for a pairproduction dominates, but the state and measurement angles used at this detection efficiency also contribute to the smallness of this number.)…”

Section: Statistical Significance and Run Timementioning

confidence: 99%

“…The fair-sampling loophole has been closed for atoms [27][28][29], superconducting qubits [30], and NV centers [22]. Using superconducting detectors, it has also been closed for photons [20,21,31,32]. The fair-coincidence assumption states that the statistics of the identified pairs are sufficiently representative of the statistics of all detected pairs, had they been correctly identified.…”

Section: The Fair-sampling (Detection) Loopholementioning

confidence: 99%

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Requirements for a loophole-free photonic Bell test using imperfect setting generators

et al. 2016

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Experimental violations of Bell inequalities are in general vulnerable to so-called "loopholes." In this work, we analyse the characteristics of a loophole-free Bell test with photons, closing simultaneously the locality, freedom-of-choice, fair-sampling (i.e. detection), coincidence-time, and memory loopholes. We pay special attention to the effect of excess predictability in the setting choices due to non-ideal random number generators. We discuss necessary adaptations of the CH/Eberhard inequality when using such imperfect devices and -using Hoeffding's inequality and Doob's optional stopping theorem -the statistical analysis in such Bell tests.

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“…In search of closing loopholes a recent Bell experiment of the group [170] closed the fair-sampling loophole, i.e., their results of violating an inequalityà la Eberhard [171] were valid without assuming that the sample of measured photons accurately represented the entire ensemble.…”

Section: Third Generation Experiments Of the Nineties And Beyondmentioning

confidence: 99%

Bell’s Universe: A Personal Recollection

Bertlmann

2016

Quantum [Un]Speakables II

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My collaboration and friendship with John Bell is recollected. I will explain his outstanding contributions in particle physics, in accelerator physics, and his joint work with Mary Bell. Mary's work in accelerator physics is also summarized. I recall our quantum debates, mention some personal reminiscences, and give my personal view on Bell's fundamental work on quantum theory, in particular, on the concept of contextuality and nonlocality of quantum physics. Finally, I describe the huge influence Bell had on my own work, in particular on entanglement and Bell inequalities in particle physics and their experimental verification, and on mathematical physics, where some geometric aspects of the quantum states are illustrated.

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Bell violation using entangled photons without the fair-sampling assumption

Cited by 517 publications

References 34 publications

The ultimate physical limits of privacy

The ultimate physical limits of privacy

Requirements for a loophole-free photonic Bell test using imperfect setting generators

Bell’s Universe: A Personal Recollection

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