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
%%%%%%%%%
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.
Hi all,
Tomorrow we will hear from Sébastien Garmier on "The Shadow of a Rotating
Black Hole". See below for the abstract. We start at 2pm on zoom:
https://ethz.zoom.us/j/362994444
Best,
Joe
Abstract:
The aim of this work is to provide an introduction to the field of shadows
of
rotating Kerr black holes. We review the mathematics of light propagation
in Kerr spacetime and derive the equations describing the edge of a Kerr
black hole shadow in the sky of a distant observer. We also discuss recent
research concerning the possibility of determining the spin parameter a and
the inclination angle $θ_O$ of the observer from direct observations
of the shadow. Finally, we showcase two applications of the theory of black
hole shadows to the Event Horizon Telescope collaboration image of the
supermassive black hole M87*.
Hi all,
Tomorrow we again have two speakers. Caroline Tornow will talk about
"Improving Quantum Applications with Pulse-Level Compilation", and Clemens
Giuliani will talk about "Variational Simulation of Quantum Circuits with
Entangled-Plaquette States". See below for their abstracts. We'll start at
2pm on zoom: https://ethz.zoom.us/j/362994444
Best,
Joe
Speaker:
Caroline Tornow
Title:
Improving Quantum Applications with Pulse-Level Compilation
Abstract:
The performance of near-term quantum algorithms, like the Quantum
Approximate Optimization Algorithm, on state-of-the-art quantum computers
is still significantly limited by noise. These algorithms are typically
represented by quantum circuits in which unitary gates process the
information. On the hardware level, these gates are implemented with
calibrated control pulses. We demonstrate a novel pulse-efficient circuit
transpilation methodology with Qiskit on IBM Quantum Computers, which
scales cross-resonance entangling pulses to reduce the total duration of
the quantum circuit in comparison to a Controlled-NOT (CNOT)-based quantum
circuit. This procedure therefore makes a better usage of the finite qubit
coherence time. By leveraging Cartan’s decomposition of SU(4) gates, we
realize arbitrary pulse-scaled two-qubit gates and benchmark our technique
on IBM Quantum devices using quantum process tomography. For almost all
implementations we observe a significant error reduction of the
pulse-efficient quantum gates in comparison to the respective CNOT
gate-based implementations. As a sample application of the pulse-efficient
methodology we implement circuits of a depth-one Quantum Approximate
Optimization Algorithm applied to the Maximum Cut optimization problem for
a non-hardware native 11-qubit graph. Here, we find that the circuit pulse
duration is decreased by up to 52% and the error is reduced by up to 38%.
Speaker:
Clemens Giuliani
Title:
Variational Simulation of Quantum Circuits with Entangled-Plaquette States
Abstract:
While it is largely believed that the classical simulation of general large
quantum circuits is hard to achieve it is often the case that specific
quantum circuits can be approximated with classical variational algorithms.
Variational representations used so far comprise tensor networks as well as
neural network quantum states based on shallow architectures. In this work
we introduce a simulation strategy for quantum circuits based on a
different Ansatz called entangled- plaquette states (EPS), which have
previously been used for simulating quantum systems on a lattice. Within
this representation, we outline which classes of quantum gates can be
applied exactly or approximately and give examples for both qubit and
photonic quantum circuits. As an application we demonstrate that EPS can in
principle be used to simulate the quantum approximate optimization
algorithm. Furthermore we extend the previous variational fidelity
optimization to wavefunctions which can be zero and present an
implementation of the stochastic reconfiguration optimization algorithm
with automatic differentiation.
Hi all,
Tomorrow we begin the season of many master students finishing their thesis
projects, in view of starting or applying to new positions in the fall. We
will therefore have two talks in the seminar for the next few weeks. We
kick it off with Nicola Quadri and Oriel Kiss, who both did their projects
at IBM. See below for the titles and abstracts of their talks. We start at
the usual time and "place", 2pm on zoom: https://ethz.zoom.us/j/362994444.
Best,
Joe
%%%%%%%%%
*Speaker:* Nicola Quadri
*Title:* Variational real-time evolution of U(1)-lattice gauge theories on
digital quantum computers
*Abstract: *Gauge theories are essential for describing the fundamental
interactions between particles in the Standard Model. However, simulating
real-time dynamics in gauge theories remains the most challenging task for
classical computers, since the dimension of the Hilbert space grows
exponentially with the system size. Quantum computers can offer a decisive
alternative, as the quantum resources required to simulate an exponentially
growing Hilbert space only increase polynomially. In this context, many
hybrid quantum-classical algorithms—or variational quantum algorithms
(VQAs)—have been developed in recent years to exploit the current noisy
quantum hardware. One of the most promising algorithms in terms of
simulating the real-time evolution of a quantum system is the variational
time evolution (VTE), which may require significantly less quantum
resources than the Trotterization method that is conventionally employed
for quantum dynamics simulations. However, this poses the main problem of
finding a variational ansatz that is able to describe the exact state along
the entire evolution. We explore the VTE of abelian gauge theories, such as
quantum electrodynamics (QED), for a (1+1)-spacetime dimensional lattice.
We first discretize and encode continuous QED on qubits. Then, we compare
the performance of the VTE using a physically motivated variational
ansatz—used so far for stationary VQAs—with the Trotterization method for a
growing system size.
*Speaker: *Oriel Kiss
*Title:* Quantum Neural Networks for electronic structure calculations
*Abstract: *In a supervised learning setting, Quantum Neural Networks
(QNNs) are quantum machine learning models described by the expectation
value of some observable with respect to a quantum state expressed by a
Parametrized Quantum Circuit (PQC). In this talk, we present a popular
strategy to design this PQC, consisting of alternating encoding and
variational layers, and apply this model to the computation of the
potential energy surface and forces field for simple molecules. In
chemistry applications, these can be used to drive molecular dynamics by
integrating the equations of motion. We investigate the performances of our
method in terms of accuracy and complexity, which are competitive with
classical counterparts. In fact, QNNs can potentially achieve very high
effective dimensions in model space, thus suggesting that they might be
well suited to tackle complex learning tasks.
Hi all,
Tomorrow we will hear from Fereshte Mozafari, who is visiting from EPFL and
working with Yuxiang, on "Preparing uniform quantum states using Boolean
methods". See below for the abstract. We start at 2pm on zoom:
https://ethz.zoom.us/j/362994444
Best,
Joe
Abstract:
A quantum algorithm to solve a specific problem is often described in terms
of a quantum circuit and some quantum algorithms require a specific quantum
state at the beginning of the computation. Therefore, efficient quantum
state preparation is an important task. The preparation of quantum states
is performed by a quantum circuit consisting of Controlled-NOT (CNOT) and
single-qubit gates. Known algorithms to prepare arbitrary quantum states
with n qubits create quantum circuits with O(2n) runtime and CNOTs that are
relatively expensive over single-qubit gates in NISQ architectures. To
reduce runtime and the number of CNOTs, we simplify the problem by only
considering an important family of quantum states, which are Uniform
Quantum States (UQSs). We map UQSs to Boolean functions and propose a
Boolean method to prepare them. Our method simplifies the problem and
enables us to apply well-understood techniques from logic synthesis.
Hi all,
This week Janek Denzler will tell us about his master thesis, entitled
Semi-device-independent
self-testing of unipartite systems based on contextuality. See below for
the abstract. We start as usual at 2pm on zoom:
https://ethz.zoom.us/j/362994444.
Best,
Joe
Abstract:
Self-testing aims to characterize adversarial input-output devices from a
minimal set of assumptions, by only interacting with the device
classically. The vast majority of protocols rely on Bell non-locality and
impose that the device be split into two non-communicating sub-devices.
This talk will explore self-testing in a single verifier setting, where our
device does not generate entanglement. This forces us to give up
device-independence. We discuss the assumptions required by protocols based
on the violation of non-contextuality inequalities, some of which are
unphysical, and propose a new set of assumptions that facilitate robust
self-testing of a unipartite system. Our protocol features a robust
quantumness certificate, based on Spekkens contextuality.
Dear all,
We have this talk on quantum startup bootcamps today at 4pm!
https://ethz.zoom.us/j/68223543732 <https://ethz.zoom.us/j/68223543732>
Best,
Lídia
Quantum Futures is a seminar series organized by the ETH Zurich Quantum
Center, with a focus on careers in quantum technologies. We talk to
academics, startups, established companies and quantum research centers
around the world to bring you career advice and news of job
opportunities. If you missed it, you can watch the first edition (an
interview with professors Yiwen Chu and Renato Renner) on ourYouTube
channel <https://www.youtube.com/channel/UCJa7n2dv7ZtdG--Ki-oMNHw>.
*Coming up on the 30th of April: a bootcamp for quantum startups!*
Would you like to venture into the world of startups? Perhaps you have a
research idea that could be turned into a company, or maybe you'd just
like to meet like-minded researchers and students and join them in such
a project? There are now startup incubators dedicated to quantum
technologies!
The Quantum Center welcomes Sam Kearney and Sean Oh for a presentation
of the Quantum Stream of the Creative Destruction Labs in Toronto.
The CDL is a non-profit organization that hosts a series of year-long
programs to train founders and connect them to mentors in industry and
academia, with the goal of forming companies to explore ideas in quantum
technologies and computing. Applications are now open for the next batch
of the bootcamp (deadline 23rd of May), and in this seminar we will
learn how the program works and how to apply. Two key aspects are that
the program is free for founders, and that you don't need a concrete
idea to apply. You can consult theCDL Quantum Stream Summary
<https://sgnldrp.online/click?redirect=https%3A%2F%2Fdrive.google.com%2Ffile…>,
theList of mentors in the Quantum Program
<https://sgnldrp.online/click?redirect=https%3A%2F%2Fwww.creativedestruction…>and
the List of CDL Quantum alumni
<https://sgnldrp.online/click?redirect=https%3A%2F%2Fwww.creativedestruction…>.
*When:*Friday, 30th of April, 4pm
*Duration:*45min
*Where:*Zoom (https://ethz.zoom.us/j/68223543732
<https://ethz.zoom.us/j/68223543732>) and YouTube
(https://www.youtube.com/channel/UCJa7n2dv7ZtdG--Ki-oMNHw
<https://www.youtube.com/channel/UCJa7n2dv7ZtdG--Ki-oMNHw>). The
recording will be available on YouTube after the seminar.
*Audience:*students and researchers in quantum science and technologies
/What is the Quantum Center?/
The freshly launchedQuantum Center <http://www.qc.ethz.ch/>is a network
of 28 research groups from ETH Zurich and PSI. The center coordinates
the various scientific and structural activities in quantum science and
technology at ETH Zurich. In particular, it interconnects research and
teaching across ETH departments and further strengthens current
activities by leveraging the broad competencies available at ETH Zurich.
You can follow us on Twitter @ETHQuantumCntr and sign up to theQuantum
Center Newsletter <https://qc.ethz.ch/news-events/mailing-list.html>to
stay in touch and learn about upcoming activities.