Hi all,
Tomorrow Severin Tschui will present his master's thesis with Zhikuan Zhao
from the computer science department, entitled "Supervised Classification
with Quantum Embeddings", and Arman Pour Tak Dost will present his semester
project with Mischa, entitled "Quasi-Ideal clocks and their environments".
See below for their abstracts. We'll start at 2pm on zoom:
https://ethz.zoom.us/j/362994444.
Best,
Joe
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Speaker: Severin Tschui
Title: Supervised Classification with Quantum Embeddings
Abstract: The theory of supervised classification using quantum algorithms
is reviewed, focusing on the similarity between classical kernel machines
and a quantum classifier model. The model is based on identifying the
encoding of classical data in a quantum Hilbert space as a feature map,
termed quantum embedding. An ansatz is defined on how to realise such an
embedding using quantum circuits, and a code framework is provided which
handles the implementation and simulation. We apply the model to classify
four different data sets, finding that it reaches high training accuracy in
all cases but failing to generalise on two data sets with greater
dimension. We present a novel idea for assessing quantum embedding quality
and carry out a simulation to investigate its merits. The experiment did
not deliver statistically significant results to confirm or refute if the
method is viable.
Speaker: Arman Pour Tak Dost
Title: Quasi-Ideal clocks and their environments
Abstract: In this presentation, we motivate the axioms that clocks should
satisfy. They were already known but motivated from a different point of
view. It turns out that quantum clocks are more precise than classical
clocks. We want to investigate the physicality of this result and present
different approaches. We find a collision model that could potentially
realize the clock experimentally. Yet, there is a rescaling procedure
involved, the physicality of which remains for further investigations.
Hi all,
Tomorrow we have two master students finishing up, Julian Schuhmacher, who
was at IBM with Ivano Tavernelli, and Yanglin Hu, who was working with
Mischa. See below for their titles and abstracts. We'll start at 2pm on
zoom: https://ethz.zoom.us/j/362994444
Best,
Joe
Speaker: Julian Schuhmacher
Title: Towards large scale simulations with quantum computers and machine
learning potentials
Abstract:The simulation of materials with molecular dynamics (MD)
simulations is an important tool to understand and predict the properties
of materials. Historically, accurate MD simulations were driven by
computationally costly, yet still approximated, first-principles electronic
structures calculations like Density Functional Theory (DFT), and therefore
were limited to small system sizes and short simulation times. In the last
few years, the application of machine learning potentials, trained on DFT
or post-Hartree Fock data, allowed to run MD simulations at the accuracy of
ab initio methods, but at a fraction of the computational cost.
Speaker: Yanglin Hu
Title: Feasibility of Experimental Realizations of Quantum Effects in
Gravitational Time Dilation
Abstract: A potentially detectable quantum discrepancy to time dilation in
delocalized clocks was derived previously. However, no experiment was put
forward to experimentally test it. In this work, we investigate the
possibility to conduct a real experiment. The expectation value and the
variance of the quantum discrepancy are derived with the Lindblad equation
and second-order perturbation theory. Two experimental protocols based on
Strontium and Magnesium optical lattice clocks are proposed. Numerical
results show that it would be possible to detect the quantum discrepancy
with next-generation Magnesium optical lattice clocks. We also investigate
the effect of decoherence mechanisms on clock's accuracy. Upper bounds on
decoherence rates in order to detect the quantum discrepancy are also
given.
Hi all,
Tomorrow our new postdoc Vilasini will tell us about "Causality and its
compatibility with space-time structure". See below for the abstract. We
start at 2pm on zoom: https://ethz.zoom.us/j/362994444.
Best,
Joe
Abstract:
We often do not distinguish between the directions of causation and
(space-)time, even though causality can be defined operationally and
independent of a space-time structure. Separating the concepts of causality
and space-time and characterising how they fit together would give crucial
insights into the different notions of causality such as operational
causality, relativistic causality and logical consistency. Motivated by
this, we develop a causal modelling framework for operationally
characterising causation in the presence of cyclic, fine-tuned and
non-classical causal influences. In the process, we distinguish between two
kinds of causal loops that can arise in our framework, depending on
operational detectability. We then define how this general class of causal
models can be embedded “compatibly” in a space-time structure i.e., without
leading to signalling outside the future. We derive necessary and
sufficient conditions for a causal model to be compatible with an embedding
in a space-time structure, and to rule out certain kinds of causal loops in
the model. In particular, this provides an operational framework for
analysing causality in the post-quantum “jamming” theories proposed in
[1,2], and generalises their results from Bell-type scenarios to arbitrary
causal structures. Furthermore, we show that post-quantum jamming can lead
to superluminal signalling, contrary to the claims of [1,2], we identify
missing assumptions in these claims as well as new features of post-quantum
theories that admit jamming non-local correlations.
Joint work with Roger Colbeck.
[1] Grunhaus, J., Popescu, S., Rohrlich, D. Phys. Rev. A53, 3781–3784
(1996).
[2] Horodecki, P. , Ramanathan, R. Nat. Comms. 10, 1701 (2019).
Hi all,
Tomorrow we will hear from two speakers, Martina Niggli and Aaron Leu, on
their master thesis and semester project, respectively. See below for the
titles and abstracts. We start at the usual time, 2pm on zoom:
https://ethz.zoom.us/j/362994444.
Best,
Joe
Speaker: Martina Niggli
Title: Quantum State Discrimination: Global Measurements vs. One-way LOCC
Abstract: The task of quantum state discrimination is considered in two
different setups: First, we analyze the setup where one party is provided
with a quantum system that was prepared in one of two states at random. We
review the optimal measurement to distinguish between the two states, the
Helstrom measurement, and we provide a theorem that characterizes the set
of all optimal measurements. Second, we look at the setup where each of two
spatially separated parties is provided with one part of a composite
system, which was prepared in one of two possible states. The two parties
are restricted to one-way LOCC strategies in order to determine the state
of their shared system. We review a known optimal strategy for pure states,
and we provide a new strategy that can be applied for arbitrary states. The
success probability of this new strategy is compared to that of a global
Helstrom measurement for different types of states, and we characterize
conditions under which the new strategy performs optimally.
Speaker: Aaron Leu
Title: Information-to-work conversion
Abstract:
As stated in the formulation of the second law of thermodynamics by Kelvin
and Plank, it is impossible to convert heat directly into work. However, it
has been known for more than 50 years that one can use information to
extract work out of a heat reservoir, but it has only been implemented
experimentally a few years ago. In most of the experiments they were able
to measure or calculate the extracted work, but they did not describe
information flows at all. The characterisation of the information was
hardly possible, because feedback control was required. In order to
describe the whole system with all its energy and information flows, we
need a closed autonomous quantum system. A broad variety of Quantum
technologies provide us with a lot of different tools, advantages and
disadvantages. Our goal is to find a platform to implement an
information-to-work protocol, which fulfills our requirements and is
experimentally feasible. We restrict ourselves to quantum technologies that
are available at the ETH, such that we can start a collaboration for an
experimental realization in the future.