Estimating exact energies in quantum simulation without Toffoli gates

Mark Steudtner, Stephanie Wehner

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)


Qubitization is a modern approach to estimate Hamiltonian eigenvalues without simulating its time evolution. While in this way approximation errors are avoided, its resource and gate requirements are more extensive: qubitization requires additional qubits to store information about the Hamiltonian, and Toffoli gates to probe them throughout the routine. Recently, it was shown that storing the Hamiltonian in a unary representation can alleviate the need for such gates in one of the qubitization subroutines. Building on that principle, we develop an alternative decomposition of the entire algorithm: without Toffoli gates, we can encode the Hamiltonian into qubits within logarithmic depth.

Original languageEnglish
Article number052329
Number of pages9
JournalPhysical Review A
Issue number5
Publication statusPublished - 2020


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