Hiroo Azuma

Interaction-free generation of entanglement

In this paper, we study the generation of entanglement by interaction-free measurements. Using Kwiat et al.s interferometer, we construct a two-qubit quantum gate that changes one particles trajectory according to the other particles trajectory. We propose methods for generating the Bell state from an electron and a positron and from a pair of photons using this gate. We also show that, by using this gate, we can carry out the Bell measurement with a probability of 3/4 at the maximum and execute a controlled-NOT operation by the method proposed by Gottesman and Chuang with a probability of 9/16 at the maximum. We estimate the success probability for generating the Bell state by our procedure under imperfect interaction.

Interaction-free quantum computation

In this paper, we study the quantum computation realized by an interaction-free measurement (IFM). Using the interferometer of Kwiat et al., we construct a two-qubit quantum gate that changes one particles trajectory according to whether or not the other particle exists in the interferometer. We propose a method for distinguishing Bell-basis vectors, each of which consists of a pair of an electron and a positron, by this gate. (This is called the Bell-basis measurement.) This method succeeds with probability 1 in the limit of N{yields}{infinity}, where N is the number of beam splitters in the interferometer. Moreover, we can carry out a controlled-NOT gate operation by the above Bell-basis measurement and the method proposed by Gottesman and Chuang. Therefore, we can prepare a universal set of quantum gates by the IFM. This means that we can execute any quantum algorithm by the IFM.

Dynamics of the Bloch vector in the thermal Jaynes-Cummings model

In this paper, we investigate the dynamics of the Bloch vector of a single two-level atom which interacts with a single quantized electromagnetic field mode according to the Jaynes-Cummings model, where the field is initially prepared in a thermal state. The time evolution of the Bloch vector

Probe and information recording/reproduction apparatus using the same

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Encryption method and apparatus encrypting and adding signature information to qubits

seems to be in complete disorder because of the thermal distribution of the initial state of the field. Both the norm and the direction of

Quantum-state-generating apparatus, Bell measurement apparatus, quantum gate apparatus, and method for evaluating fidelity of quantum gate

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Method and apparatus for configuring quantum mechanical state, and communication method and apparatus using the same

oscillate hard and their periods seem infinite. We observe that the trajectory of the time evolution of

Decoherence in Grover's quantum algorithm: Perturbative approach

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Image display apparatus with getter scattering prevention

in the two- or three-dimensional space does not form a closed path. To remove the fast frequency oscillation from the trajectory, we take the time average of the Bloch vector

Interaction-free measurement with an imperfect absorber

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