Vittorio Vitale, Andreas Elben, Richard Kueng, Antoine Neven, Jose Carrasco, Barbara Kraus, Peter Zoller, Pasquale Calabrese, Benoit Vermersch, Marcello Dalmonte
SciPost Phys. 12, 106 (2022) ·
published 25 March 2022
|
· pdf
When a quantum system initialized in a product state is subjected to either
coherent or incoherent dynamics, the entropy of any of its connected partitions
generically increases as a function of time, signalling the inevitable
spreading of (quantum) information throughout the system. Here, we show that,
in the presence of continuous symmetries and under ubiquitous experimental
conditions, symmetry-resolved information spreading is inhibited due to the
competition of coherent and incoherent dynamics: in given quantum number
sectors, entropy decreases as a function of time, signalling dynamical
purification. Such dynamical purification bridges between two distinct short
and intermediate time regimes, characterized by a log-volume and log-area
entropy law, respectively. It is generic to symmetric quantum evolution, and as
such occurs for different partition geometry and topology, and classes of
(local) Liouville dynamics. We then develop a protocol to measure
symmetry-resolved entropies and negativities in synthetic quantum systems based
on the random unitary toolbox, and demonstrate the generality of dynamical
purification using experimental data from trapped ion experiments [Brydges et
al., Science 364, 260 (2019)]. Our work shows that symmetry plays a key role as
a magnifying glass to characterize many-body dynamics in open quantum systems,
and, in particular, in noisy-intermediate scale quantum devices.
Antoine Neven, David Gunn, Martin Hebenstreit, Barbara Kraus
SciPost Phys. 11, 042 (2021) ·
published 30 August 2021
|
· pdf
Understanding multipartite entanglement is vital, as it underpins a wide
range of phenomena across physics. The study of transformations of states via
Local Operations assisted by Classical Communication (LOCC) allows one to
quantitatively analyse entanglement, as it induces a partial order in the
Hilbert space. However, it has been shown that, for systems with fixed local
dimensions, this order is generically trivial, which prevents relating
multipartite states to each other with respect to any entanglement measure. In
order to obtain a non-trivial partial ordering, we study a physically motivated
extension of LOCC: multi-state LOCC. Here, one considers simultaneous LOCC
transformations acting on a finite number of entangled pure states. We study
both multipartite and bipartite multi-state transformations. In the
multipartite case, we demonstrate that one can change the stochastic LOCC
(SLOCC) class of the individual initial states by only applying Local Unitaries
(LUs). We show that, by transferring entanglement from one state to the other,
one can perform state conversions not possible in the single copy case; provide
examples of multipartite entanglement catalysis; and demonstrate improved
probabilistic protocols. In the bipartite case, we identify numerous
non-trivial LU transformations and show that the source entanglement is not
additive. These results demonstrate that multi-state LOCC has a much richer
landscape than single-state LOCC.
Dr Neven: "We are grateful to the referee..."
in Submissions | report on Local Transformations of Multiple Multipartite States