title: Realization of quantum digital signatures without the requirement of quantum memory.
abstract: Digital signatures are widely used to provide security for electronic communications, for example, in financial transactions and electronic mail. Currently used classical digital signature schemes, however, only offer security relying on unproven computational assumptions. In contrast, quantum digital signatures offer information-theoretic security based on laws of quantum mechanics. Here, security against forging relies on the impossibility of perfectly distinguishing between nonorthogonal quantum states. A serious drawback of previous quantum digital signature schemes is that they require long-term quantum memory, making them impractical at present. We present the first realization of a scheme that does not need quantum memory and which also uses only standard linear optical components and photodetectors. In our realization, the recipients measure the distributed quantum signature states using a new type of quantum measurement, quantum state elimination. This significantly advances quantum digital signatures as a quantum technology with potential for real applications.
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Collins
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Donaldson
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom and School of Informatics, Informatics Forum, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, United Kingdom and Laboratory of Evolutionary Genetics, Division of Molecular Biology, Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia.
authors.forename: Vedran
authors.initials: V
authors.lastname: Dunjko
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Petros
authors.initials: P
authors.lastname: Wallden
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Clarke
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Erika
authors.initials: E
authors.lastname: Andersson
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Jeffers
authors.affiliation: SUPA, Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, David Brewster Building, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Buller