Experimental Quantum Coin Tossing

Molina‐Terriza, Gabriel; Vaziri, Alipasha; Ursin, Rupert; Zeilinger, Anton

doi:10.1103/physrevlett.94.040501

Cited by 144 publications

(137 citation statements)

References 17 publications

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“…There, different multilevel degrees of freedom, such as spatial modes (13), time-energy (14), path (15,16), as well as continuous variables (17,18), have been used. Entanglement of spatial modes of photons has especially attracted much attention in recent years (19)(20)(21)(22)(23)(24)(25)(26)(27)(28), because it is readily available from optical nonlinear crystals and the number of involved modes of the entanglement can be very high (29).…”

mentioning

confidence: 99%

Generation and confirmation of a (100 × 100)-dimensional entangled quantum system

Krenn

Huber

Fickler

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

305

254

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Entangled quantum systems have properties that have fundamentally overthrown the classical worldview. Increasing the complexity of entangled states by expanding their dimensionality allows the implementation of novel fundamental tests of nature, and moreover also enables genuinely new protocols for quantum information processing. Here we present the creation of a (100 × 100)-dimensional entangled quantum system, using spatial modes of photons. For its verification we develop a novel nonlinear criterion which infers entanglement dimensionality of a global state by using only information about its subspace correlations. This allows very practical experimental implementation as well as highly efficient extraction of entanglement dimensionality information. Applications in quantum cryptography and other protocols are very promising.photonic spatial modes | quantum optics | Schmidt rank | entanglement witness Q uantum entanglement of distant particles leads to correlations that cannot be explained in a local realistic way (1-3). To obtain a deeper understanding of entanglement itself, as well as its application in various quantum information tasks, increasing the complexity of entangled systems is important. Essentially, this can be done in two ways. The first method is to increase the number of particles involved in the entanglement (4). The alternative method is to increase the entanglement dimensionality of a system.Here we focus on the latter one, namely on the dimension of the entanglement. The text is structured as follows. After a short review of properties and previous experiments, we present a unique method to verify high-dimensional entanglement. Then we show how we experimentally create our high-dimensional two-photon entangled state. We analyze this state with our method and verify a 100 × 100-dimensional entangled quantum system. We conclude with a short outlook to potential future investigations.High-dimensional entanglement provides a higher information density than conventional two-dimensional (qubit) entangled states, which has important advantages in quantum communication. First, it can be used to increase the channel capacity via superdense coding (5). Second, high-dimensional entanglement enables the implementation of quantum communication tasks in regimes where mere qubit entanglement does not suffice. This involves situations with a high level of noise from the environment (6, 7), or quantum cryptographic systems where an eavesdropper has manipulated the random number generator involved (8). Moreover, the entangled dimensions of the whole Hilbert space also play a very interesting role in quantum computation: high-dimensional systems can be used to simplify the implementation of quantum logic (9). Furthermore, it has been found recently (10) that any continuous measure of entanglement (such as concurrence, entanglement of formation, or negativity) can be very small, while the quantum system still permits an exponential computation speedup over classical machines. This is not the case for the dim...

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mentioning

confidence: 99%

Generation and confirmation of a (100 × 100)-dimensional entangled quantum system

Krenn

Huber

Fickler

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

305

254

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“…As a way to account for errors, the related primitive of bit string generation was also considered [20][21][22] . In practice, a first implementation concerned a protocol that becomes insecure for any loss 23 , while a promising solution gave results that unfortunately cannot be used in realistic conditions 24 . More recently, an implementation of the loss-tolerant protocol 25 used an entangled-photon source to eliminate the problem of multiphoton pulses.…”

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confidence: 99%

Experimental plug and play quantum coin flipping

et al. 2014

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Performing complex cryptographic tasks will be an essential element in future quantum communication networks. These tasks are based on a handful of fundamental primitives, such as coin flipping, where two distrustful parties wish to agree on a randomly generated bit. Although it is known that quantum versions of these primitives can offer informationtheoretic security advantages with respect to classical protocols, a demonstration of such an advantage in a practical communication scenario has remained elusive. Here we experimentally implement a quantum coin flipping protocol that performs strictly better than classically possible over a distance suitable for communication over metropolitan area optical networks. The implementation is based on a practical plug and play system, developed by significantly enhancing a commercial quantum key distribution device. Moreover, we provide combined quantum coin flipping protocols that are almost perfectly secure against bounded adversaries. Our results offer a useful toolbox for future secure quantum communications.

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“…We report elsewhere [14] an experimental realisation of quantum bit-string generation, based on the protocol and security analysis presented here. We note that another experiment realising quantum coin tossing has recently been reported [15]. This experiment is an impressive achievement from the point of view of physics (for example, it is one of the first to realise individual control over quantum qutrits).…”

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confidence: 95%

Security of quantum bit-string generation

Barrett

Massar

2004

Phys. Rev. A

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We consider the cryptographic task of bit-string generation. This is a generalisation of coin tossing in which two mistrustful parties wish to generate a string of random bits such that an honest party can be sure that the other cannot have biased the string too much. We consider a quantum protocol for this task, originally introduced in Phys. Rev. A 69, 022322 (2004), that is feasible with present day technology. We introduce security conditions based on the average bias of the bits and the Shannon entropy of the string. For each, we prove rigorous security bounds for this protocol in both noiseless and noisy conditions under the most general attacks allowed by quantum mechanics. Roughly speaking, in the absence of noise, a cheater can only bias significantly a vanishing fraction of the bits, whereas in the presence of noise, a cheater can bias a constant fraction, with this fraction depending quantitatively on the level of noise. We also discuss classical protocols for the same task, deriving upper bounds on how well a classical protocol can perform. This enables the determination of how much noise the quantum protocol can tolerate while still outperforming classical protocols. We raise several conjectures concerning both quantum and classical possibilities for large n cryptography. An experiment corresponding to the scheme analysed in this paper has been performed and is reported elsewhere.

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Experimental Quantum Coin Tossing

Cited by 144 publications

References 17 publications

Generation and confirmation of a (100 × 100)-dimensional entangled quantum system

Generation and confirmation of a (100 × 100)-dimensional entangled quantum system

Experimental plug and play quantum coin flipping

Security of quantum bit-string generation

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