| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for verifying a quantum entanglement conditions which are shared by n quanta. SOLUTION: A symbol ¾<SB>Ψ</SB>> representing an inter-n-quantum state (n≥3) used in a projector is divided into two groups by means of possible 2<SP>n-1</SP>-1 kinds of methods, and entanglement index is computed for each divided group. The classes S (k<SB>1</SB>, ..., k<SB>m</SB>) of entanglements to be distinguished are set from values k<SB>t</SB>which are lower than the entanglement indexes of the divided groups (1≤t≤2<SP>n-1</SP>-1 and m=2<SP>n-1</SP>-1). The maximum fidelity is found by calculating equation c=max<SB>ρES(k1, ..., km)</SB><<SB>Ψ</SB>¾ρ¾<SB>Ψ</SB>> (where<SB>E</SB>represents a set symbol). An entanglement verification operator W=cI-¾<SB>Ψ</SB>><<SB>Ψ</SB>¾ is measured with respect to the inter-n-quantum state to be measured to compute the expectation value Tr(Wρ)<SB>exp</SB>of Tr(Wρ), (I represents unit matrix). Whether the Tr(Wρ)<SB>exp</SB>is larger than 0 is determined, to verify the quantum entanglement state of the quantum stateρ. COPYRIGHT: (C)2007,JPO&INPIT
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