Quantum algorithm for measuring the energy of n qubits with unknown pair-interactions

  • Authors:

  • Dominik Janzing

  • Affiliations:

  • Institut für Algorithmen und Kognitive Systeme, Arbeitsgruppe Quanten Computing, Universität Karlsruhe, Karlsruhe, Germany

  • Venue:
  • Quantum Information & Computation
  • Year:
  • 2002

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Abstract

The well-known algorithm for quantum phase estimation requires that the considered unitary is available as a conditional transformation depending on the quantum state of an ancilla register. We present an algorithm converting an unknown n-qubit pair-interaction Hamiltonian into a conditional one such that standard phase estimation can be applied to measure the energy. Our essential assumption is that the considered system can be brought into interaction with a quantum computer. For large n the algorithm could still be applicable for estimating the density of energy states and might therefore be useful for rinding energy gaps in solid states.