DigitalAnalog Quantum Computing: a Paradigm for the NISQ Era
DIPC Seminars
 Speaker

Mikel Sanz, QUTIS, UPVEHU Leioa
 When

2019/02/22
13:00  Place
 Donostia International Physics Center
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Purely digital classical computers are rather recent devices which are a
consequence of the impressive technological development in miniaturization of
electronics and microchips. However, until only few decades ago, digital
computers had not sufficient computational power for most applications, so
they usually employed analog parts for specific hard calculations. The
situation nowadays in quantum computing is similar due to the small number of
coherent controllable qubits allowed by current platforms. Even doubling the
number of qubits yearly, a purely digital approach with error correction will
not allow us to solve relevant problems in the following decades. Here, we
will explore in detail a universal digitalanalog approach employing the
ubiquitous Ising Hamiltonian as the resource. We use this global Hamiltonian,
together with local rotations, to generate an arbitrary unitary and we find
efficient protocols, polynomial in the number of singlequbit rotations, to
produce relevant families of Hamiltonian, such as arbitrary twobody
Hamiltonians or, in general, kbody Hamiltonians. We introduce the concept of
banged digitalanalog quantum computing, in opposition to the stepwise, when
singlequbit rotations are much faster than the natural timescale of the
Hamiltonian, which allows us to compute without switching on/off the global
interaction. Employing natural models of errors, we compare the performance of
digital against both stepwise and banged digitalanalog protocols showing
that, in general, digitalanalog approaches perform better both in time and
fidelity. Finally, we will also show that this emerging digitalanalog
approach can be applied not only to quantum simulations, but also to quantum
algorithms. Indeed, we provide an efficient digitalanalog description of the
Quantum Fourier transform, comparing its performance against the pure digital
approach in the presence of errors.
Bibliography:
A. ParraRodriguez, L. Lamata, P. Lougovski, E. Solano, and M. Sanz, "Digital
Analog Quantum Computing", in preparation.
L. Lamata, A. ParraRodriguez, M. Sanz, and E. Solano, "DigitalAnalog Quantum
Simulations with Superconducting Circuits", Advances in Physics: X *3*,
1457981 (2018).
J. L. Dodd, M. A. Nielsen, M. J. Bremner, and R. T. Thew, "Universal quantum
computation and simulation using any entangling Hamiltonian and local
unitaries", Phys. Rev. A 65, 040301ô°‘R (2002).ô°€
U. Las Heras, U. AlvarezRodriguez, E. Solano, and M. Sanz, "Genetic
Algorithms for Digital Quantum Simulations", Phys. Rev. Lett. 116, 230504
(2016).
A. MartÃn, I. L. Egusquiza, E. Solano, and M. Sanz, "Efficient DigitalAnalog
Algorithm for Quantum Fourier Transform". In preparation
Host: Geza Giedke