Abstract

The measurement of a quantum system’s state is of fundamental importance. In particular, determining an arbitrary state of a quantum mechanical two-level system (a qubit) is relevant in the context of quantum information processing [1]. The exact determination of a qubit’s state would require infinitely many measurements on identically prepared qubits. If a finite number N of qubits is available, an optimal estimate of the quantum state can be obtained by simultaneous measurements on all N qubits. We have performed sequential measurements on arbitrary but identically prepared states of a single qubit in order to estimate its state more economically.

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