Hi all,
Tomorrow Giulia Mazzola will tell us about her master thesis at IBM, on
"Simulating Yang-Mills Lattice Gauge Theories on Digital Quantum
Computers". See below for the abstract. Here's the link:
https://ethz.zoom.us/j/362994444.
Best,
-joe
Abstract:
Gauge theories represent the most successful description of elementary
particles and their fundamental interactions. In computing the real-time
dynamics in lattice gauge theories however, standard classical numerical
methods suffer from an exponential scaling of the required resources with
growing system size and thus, display severe limitations for the simulation
of real-time phenomena. Quantum computers might provide a potential
framework to tackle this problem as lattice gauge theories can be
efficiently represented using resources which are polynomial in the system
size. Here, we review different encoding schemes for non-abelian Yang-Mills
lattice gauge theories with dynamical fermionic matter such as quantum
chromodynamics in arbitrary dimensions on digital circuit-based quantum
computers. On the other hand, we apply promising variational quantum
algorithms for near-term quantum computation to study the groundstate
properties of small abelian lattice gauge theory systems like quantum
electrodynamics in (1+1)- and (2+1)-spacetime dimensions. Specifically, we
investigate the performance of physically motivated variational forms that
preserve the gauge symmetry of the theory, thereby allowing for an
efficient sampling in the physical Hilbert space of states. Therewith, we
demonstrate the phenomenon of flux-string breaking in form of a phase
diagram and further present the results of simulations on real
superconducting quantum hardware as a proof-of-principle. By generalizing
this scheme to non-abelian Yang-Mills theories, such gauge invariant
variational forms might be included in variational real-time evolution
algorithms, providing a potential path towards simulating real-time
dynamics of lattice gauge theories on near-term quantum devices.
Hi all,
Tomorrow Anne-Catherine de la Hamette will tell us about her master thesis
with Thomas Galley at Perimeter Institute, entitled "Quantum reference
frames: a relational approach to quantum theory". See the abstract below
for more details. Zoom link: https://ethz.zoom.us/j/362994444.
Best,
-joe
Abstract
Reference frames are essential in the description of physical phenomena.
Often used implicitly, they appear as idealized classical systems.
Following a more fundamental approach and considering them as physical
systems subject to the laws of quantum mechanics, they become quantum
reference frames (QRFs). A rigorous treatment of QRFs is indispensable both
in the construction of a relational theory of quantum mechanics and of
quantum gravity. Not only do the properties of QRFs give rise to numerous
applications in quantum information; they are also expected to improve our
understanding of observer-dependent settings such as the Wigner's friend
experiment.
In this talk, we present a relational formalism based on the group and
representation theoretic nature of reference frames. By identifying
coordinate systems with elements of a symmetry group G, we define a general
operator for reversibly transforming between QRFs associated to the group
G. We explore the properties of this operator in different cases and show
how it gives rise to transformations between coordinate systems which are
`in a superposition' relative to other coordinate systems. Finally, we
apply the relational formalism and the change of reference system developed
in this work to the Wigner's friend thought experiment.