Papers by Hitoshi Inamori
Journal of Quantum Information Science
According to quantum mechanics, the outcome of an experiment exists relative to an Experimenter w... more According to quantum mechanics, the outcome of an experiment exists relative to an Experimenter who performs a measurement on the system under study. Witnessing the outcome of an experience requires the measurement on a physical system whose size must match the complexity of the Experimenter's observation. We argue that such a physical system must have a certain space-time extension so that it can encode the rich and complex data embedded in the witnessed experience. The complementarity principle in quantum mechanics leads us to conjecture that the observable events constituting an experience have space-like separation with each other. This seems to be in contradiction with our perceived locality of physical laws, and encourages us to think that the act of measurement is not a physical process, in the sense that a measurement outcome witnessed by an Experimenter is not necessarily related to the physical description of the Experimenter observed from the outside.
Algorithmica, 2008
Abstract. We propose a proof of the security of a practical BB84 quantum key distribution protoco... more Abstract. We propose a proof of the security of a practical BB84 quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect optical devices.
Algorithmica, 2002
We propose a proof of the security of a practical BB84 quantum key distribution protocol against ... more We propose a proof of the security of a practical BB84 quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect optical devices.
Modifications to a previous proof of the security of EPR-based quantum key distribution are propo... more Modifications to a previous proof of the security of EPR-based quantum key distribution are proposed. This modified version applies to a protocol using three conjugate measurement bases rather than two. A higher tolerable error rate is obtained for the three-basis protocol.
Nature
We describe in detail a general strategy for implementing a conditional geometric phase between t... more We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.
Algorithmica, 2008
Abstract. We propose a proof of the security of a time-reversed EPR quantum key distribution prot... more Abstract. We propose a proof of the security of a time-reversed EPR quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect photon sources.
We propose a proof of the security of EPR-based quantum key distribution against enemies with unl... more We propose a proof of the security of EPR-based quantum key distribution against enemies with unlimited computational power. The proof holds for a protocol using interactive error-reconciliation scheme. We assume in this paper that the legitimate parties receive a given number of single photon signals and that their measurement devices are perfect.
Journal of Physics A-mathematical and General, 2001
We investigate a new strategy for incoherent eavesdropping in Ekert's entanglement based quantum ... more We investigate a new strategy for incoherent eavesdropping in Ekert's entanglement based quantum key distribution protocol. We show that under certain assumptions of symmetry the effectiveness of this strategy reduces to that of the original single qubit protocol of Bennett and Brassard.
International Journal of Modern Physics A, 2001
``Information is physical and any processing of information is always performed by physical means... more ``Information is physical and any processing of information is always performed by physical means,'' an innocent-sounding statement, but its consequences are profound. When quantum effects become important, for example, at the level of single atoms and photons, the classical theory of computation becomes fundamentally inadequate. Entirely new modes of computation and information processing become possible. In the last few years there has been an explosion of theoretical and experimental research in quantum computation. In this brief review we describe some of these developments.
1 Qubits, gates and networks Consider the two binary strings, 011, (1.1) 111. (1.2) The first one... more 1 Qubits, gates and networks Consider the two binary strings, 011, (1.1) 111. (1.2) The first one can represent, for example, the number 3 (in binary) and the second one the number 7. In general three physical bits can be prepared in 23 = 8 different configurations that can represent, for example, the integers from 0 to 7. However, a register composed of three classical bits can store only one number at a given moment of time. Enter qubits and quantum registers: A qubit is a quantum system in which the Boolean states 0 and 1 are represented by a prescribed pair of normalised and mutually orthogonal quantum states labeled as ∣0〉, ∣1〉 [1]. The two states form a “computational basis” and any other (pure) state of the qubit can be written as a superposition α|0〉 + β|1〉 for some α and β such that |α|2 + |β|2 = 1. A qubit is typically a microscopic system, such as an atom, a nuclear spin, or a polarised photon. A collection of n qubits is called a quantum register of size n.
Journal of Modern Optics, 2000
We describe in detail a general strategy for implementing a conditional geometric phase between t... more We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.
Journal of Modern Optics, 2000
We describe in detail a general strategy for implementing a conditional geometric phase between t... more We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.
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Papers by Hitoshi Inamori