Quantum algorithm for obtaining the energy spectrum of a physical system

Hefeng Wang, S. Ashhab, Franco Nori

Research output: Contribution to journalArticle

17 Citations (Scopus)


We present a polynomial-time quantum algorithm for obtaining the energy spectrum of a physical system, i.e., the differences between the eigenvalues of the system's Hamiltonian, provided that the spectrum of interest contains at most a polynomially increasing number of energy levels. A probe qubit is coupled to a quantum register that represents the system of interest such that the probe exhibits a dynamical response only when it is resonant with a transition in the system. By varying the probe's frequency and the system-probe coupling operator, any desired part of the energy spectrum can be obtained. The algorithm can also be used to deterministically prepare any energy eigenstate. As an example, we have simulated running the algorithm and obtained the energy spectrum of the water molecule.

Original languageEnglish
Article number062304
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number6
Publication statusPublished - 5 Jun 2012


ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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