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Performing joint measurements and transformations on several qubits by operating on a single control qubit

Dominik Janzing·Thomas Decker·Thomas Beth
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Abstract

An n-qubit quantum register can in principle be completely controlled by operating on a single qubit that interacts with the register via an appropriate fixed interaction. We consider a hypothetical system consisting of n spin-1/2 nuclei that interact with an electron spin via a magnetic interaction. We describe algorithms that measure non-trivial joint observables on the register by acting on the control spin only. For large n this is not an efficient model for universal quantum computation but it can be modified to an efficient one if one allows n possible positions of the control particle. This toy model of measurements illustrates in which way specific interactions between the register and a probe particle support specific types of joint measurements in the sense that some joint observables can be measured by simple sequences of operations on the probe particle.

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Dominik Janzing, Thomas Decker, Thomas Beth. 2002-07-23. Performing joint measurements and transformations on several qubits by operating on a single control qubit. https://doi.org/10.1103/physreva.67.042320

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