Abstract
Device-independent quantum key distribution (DIQKD) is a formalism that supersedes traditional quantum key distribution, as its security does not rely on any detailed modeling of the internal working of the devices. This strong form of security is only possible using devices producing correlations that violate a Bell inequality. Full security proofs of DIQKD have recently been reported, but they tolerate zero or small amounts of noise and are restricted to protocols based on specific Bell inequalities. Here, we provide a security proof of DIQKD that is both more efficient and noise resistant, and also more general, as it applies to protocols based on arbitrary Bell inequalities and can be adapted to cover supraquantum eavesdroppers limited by the no-signaling principle only. It is formulated, however, in the bounded-quantum-storage model, where an upper bound on the adversary’s quantum memory is a priori known. This condition is not a limitation at present, since the best existing quantum memories have very short coherence times.
- Received 9 November 2012
- Corrected 22 January 2014
DOI:https://doi.org/10.1103/PhysRevX.3.031007
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Published by the American Physical Society
Corrections
22 January 2014
Erratum
Publisher’s Note: Security of Device-Independent Quantum Key Distribution in the Bounded-Quantum-Storage Model [Phys. Rev. X 3, 031007 (2013)]
S. Pironio, Ll. Masanes, A. Leverrier, and A. Acín
Phys. Rev. X 4, 019901 (2014)
Popular Summary
The fundamental attraction of quantum key distribution (QKD) comes from the fact that any attempt by an eavesdropper to crack a properly designed quantum key leaves an indelible “fingerprint” on the quantum messages exchanged by the communicating parties (Alice and Bob). Methods of coordinated detection of such fingerprints are at the center of a QKD security proof. Until very recently, crucial assumptions that are hard to meet in practice are invariably made in the standard QKD schemes about the devices Alice and Bob use. The notion of device-independent quantum key distribution (DIQKD) has emerged as an answer to that serious practical limitation. A main open question in this new direction is this: Is a general and practical security proof possible? In this paper, we make progress toward answering this question with a strong, if not absolute, “yes.”
In a DIQKD security proof, the security of the quantum key is certified by violation of a Bell inequality. The more forms of Bell inequality a security proof applies to, the more general or powerful it then is. While removing demands on the internal working of the devices, the DIQKD security proofs proposed so far have their own practical limitations. Some of them require the use of many devices; others do not tolerate any noise. One security proof proposed by Vidick and Vazirani uses only the minimal two devices and can, in principle, tolerate noise. But, it works only for a given form of Bell inequality and for low noise levels.
By comparison, our security proof makes gain in a number of ways: (i) It requires only two devices, (ii) it applies to any Bell inequality, and (iii) it tolerates noise levels that are realistic. All these advantages come at the price of assuming that the eavesdropper does not have a long-term quantum memory. This assumption, however, is rather reasonable, given the present quantum technology. Our work then implies that secure and practical device-independent quantum key distribution becomes possible under realistic assumptions.
