Tight speed limits on two-qubit gates in a fully-connected quantum computer
ORAL
Abstract
A quantum computer with fully connected qubits is expected to perform quantum algorithms involving remote
quantum gates much faster than one with locally connected qubits. The exact amount of speedup is however
hard to quantify. Here we provide a strict upper bound of such speedup on an arbitrary two-qubit gate, for
an arbitrary number of qubits involved, and with an arbitrary time-dependent Hamiltonian containing strongly
long-range two-body interactions. The bound is tight up to a small prefactor. In addition, for an important
subclass of such Hamiltonians and SWAP gates, we obtain a bound that is quantitatively tight, the first of its
kind. This second bound is achieved via a newly developed Quantum Brachistochrone method that incorporates
inequality constraints. The bounds obtained here also pave the way towards obtaining tight Lieb-Robinson-type
bounds for strongly long-range interacting systems.
quantum gates much faster than one with locally connected qubits. The exact amount of speedup is however
hard to quantify. Here we provide a strict upper bound of such speedup on an arbitrary two-qubit gate, for
an arbitrary number of qubits involved, and with an arbitrary time-dependent Hamiltonian containing strongly
long-range two-body interactions. The bound is tight up to a small prefactor. In addition, for an important
subclass of such Hamiltonians and SWAP gates, we obtain a bound that is quantitatively tight, the first of its
kind. This second bound is achieved via a newly developed Quantum Brachistochrone method that incorporates
inequality constraints. The bounds obtained here also pave the way towards obtaining tight Lieb-Robinson-type
bounds for strongly long-range interacting systems.
*We acknowledge funding support from the NSF RAISE-TAQS program under Grant No. CCF-1839232 and the W. M.Keck Foundation.
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Presenters
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Casey W Jameson
- Colorado School of Mines