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Quantum state discrimination underlies various applications in quantum information processing tasks. It essentially describes the distinguishability of quantum systems in different states, and the general process of extracting classical information from quantum systems. It is also useful in quantum information applications, such as the characterisation of… (More)

- Joonwoo Bae, Younghun Kwon
- 2008

There are hamiltonians that solve a search problem of finding one of N items in O(√ N) steps. They are hamiltonians to describe an oscillation between two states. In this paper we propose a generalized search hamil-tonian, Hg. Then the known search hamiltonians become special cases of Hg. From the generalized search hamiltonian, we present remarkable… (More)

- Sangwoong Park, Joonwoo Bae, Younghun Kwon
- 2003

It is questionable that Grover algorithm may be more valuable than a classical one, when a partial information is given in a unstructued database. In this letter, to consider quantum search when a partial information is given, we replace the Fourier transform in the Grover algorithm with the Haar wavelet transform. We then, given a partial information L to… (More)

We consider optimal state discrimination in a general convex operational framework, so-called generalized probabilistic theories (GPTs), and present a general method of optimal discrimination by applying the complementarity problem from convex optimization. The method exploits the convex geometry of states but not other detailed conditions or relations of… (More)

We study N-dimensional measurement-device-independent quantum-key-distribution protocol where one checking state is used. Only assuming that the checking state is a superposition of other N sources, we show that the protocol is secure in zero quantum-bit-error-rate case, suggesting possibility of the protocol. The method may be applied in other quantum… (More)

- Joonwoo Bae, Younghun Kwon
- 2008

Farhi et al. suggested the analogue quantum search Hamiltonian and Fenner also proposed the intuitive quantum search Hamiltonian. Recently the generalized quantum search Hamiltonian containning hamiltonians of Farhi et al. and Fenner was presented in quant-ph/0110020. In this letter, we analyze the running time of the generalized quantum search Hamiltonian.… (More)

- Joonwoo Bae, Younghun Kwon
- 2002

In this letter, we show that the laser Hamiltonian can perform the quantum search. We also show that the process of quantum search is a resonance between the initial state and the target state, which implies that Nature already has a quantum search system to use a transition of energy. In addition, we provide the particular scheme to implement the quantum… (More)

- Joonwoo Bae, Younghun Kwon
- 2002

Quantum adiabatic evolution algorithm suggested by Farhi et al. was effective in solving instances of NP-complete problems. The algorithm is governed by the adiabatic theorem. Therefore, in order to reduce the running time, it is essential to examine the minimum energy gap between the ground level and the next one through the evolution. In this letter, we… (More)

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