scholarly journals A quantum algorithm for obtaining the energy spectrum of a physical system without guessing its eigenstates

2014 ◽  
Vol 16 (30) ◽  
pp. 16241-16245 ◽  
Author(s):  
Hefeng Wang
Keyword(s):  
Energy Spectrum ◽  
Physical System ◽  
Quantum Algorithm

We present a quantum algorithm that provides a general approach for obtaining the energy spectrum of a physical system without making a guess on its eigenstates.

scholarly journals Quantum algorithm for obtaining the energy spectrum of molecular systems

2008 ◽  
Vol 10 (35) ◽  
pp. 5388 ◽  
Author(s):  
Hefeng Wang ◽  
Sabre Kais ◽  
Alán Aspuru-Guzik ◽  
Mark R. Hoffmann
Keyword(s):  
Energy Spectrum ◽  
Quantum Algorithm ◽  
Molecular Systems

Quantum algorithm for measuring the eigenvalues of UÄU-1 for a black-box unitary transformation U

2002 ◽  
Vol 2 (3) ◽  
pp. 192-197
Author(s):  
D. Janzing ◽  
T. Beth
Keyword(s):  
Energy Spectrum ◽  
Quantum System ◽  
Autocorrelation Function ◽  
Unitary Transformation ◽  
Quantum Computer ◽  
Quantum Algorithm ◽  
Black Box ◽  
Phase Estimation

Estimating the eigenvalues of a unitary transformation U by standard phase estimation requires the implementation of controlled-U-gates which are not available if U is only given as a black box. We show that a simple trick allows to measure eigenvalues of U\otimesU^\deggar even in this case. Running the algorithm several times allows therefore to estimate the autocorrelation function of the density of eigenstates of U. This can be applied to find periodicities in the energy spectrum of a quantum system with unknown Hamiltonian if it can be coupled to a quantum computer.

Energy as an Entanglement Indicator

2011 ◽  
Vol 18 (01) ◽  
pp. 33-54
Author(s):  
Miłosz Michalski
Keyword(s):  
Energy Spectrum ◽  
Physical System ◽  
Thermal Equilibrium ◽  
Equilibrium States ◽  
Approximate Algorithm ◽  
Partial Knowledge ◽  
Heisenberg Chain ◽  
Entanglement Witness

We explore the method of constructing an entanglement witness utilising the Hamiltonian of a physical system in consideration. Already a partial knowledge of the energy spectrum allows one not only to detect entanglement in thermal equilibrium states, but also to discriminate among its various multipartite genres. We propose an efficient approximate algorithm producing a witness capable of detecting genuine n-partite entanglement. As an illustration, the method is applied to an analytically computable example of anisotropic XXZ Heisenberg chain.

The electronic energy spectrum of zero-gap semiconductors

1976 ◽  
Vol 120 (11) ◽  
pp. 337 ◽  
Author(s):  
B.L. Gel'mont ◽  
V.I. Ivanov-Omskii ◽  
I.M. Tsidil'kovskii
Keyword(s):  
Energy Spectrum ◽  
Electronic Energy ◽  
Electronic Energy Spectrum
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