Hi all,
Tomorrow our visitor from NUS Josep Lumbreras will tell us about ''Multi-armed quantum bandits'’.
See below for the abstract. The talk will take place at 2pm in HIT F31.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best,
Ladina
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Abstract:
We initiate the study of tradeoffs between exploration and exploitation in online learning of properties of quantum states. Given sequential oracle access to an unknown quantum state, in each round, we are tasked to choose an observable from a set of actions aiming to maximize its expectation value on the state (the reward). Information gained about the unknown state from previous rounds can be used to gradually improve the choice of action, thus reducing the gap between the reward and the maximal reward attainable with the given action set (the regret). We provide various information-theoretic lower bounds on the cumulative regret that an optimal learner must incur, and show that it scales at least as the square root of the number of rounds played. We also investigate the dependence of the cumulative regret on the number of available actions and the dimension of the underlying space. Moreover, we exhibit strategies that are optimal for bandits with a finite number of arms and general mixed states. If we have a promise that the state is pure and the action set is all rank-1 projectors the regret can be interpreted as the infidelity with the target state and we provide some support for the conjecture that measurement strategies with less regret exist for this case.
Hi all,
Tomorrow our visitor from NUS Roberto Rubboli will tell us about ''Fundamental Limits on Correlated Catalytic State Transformations'’.
See below for the abstract. The talk will take place at 2pm in HIT F31.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best,
Ladina
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Abstract:
Determining whether a given state can be transformed into a target state using free operations is one of the fundamental questions in the study of resources theories. Free operations in resource theories can be enhanced by allowing for a catalyst system that assists the transformation and is returned unchanged, but potentially correlated, with the target state. While this has been an active area of recent research, very little is known about the necessary properties of such catalysts. Here, we prove fundamental limits applicable to any correlated catalytic transformation by showing that a small residual correlation between catalyst and target state implies that the catalyst needs to be highly resourceful. In fact, the resources required diverge in the limit of vanishing residual correlation. We develop our results in a general resource theory framework and discuss its implications for the resource theory of athermality, the resource theory of coherence and entanglement theory.
https://arxiv.org/abs/2111.13356
Hi all,
tomorrow Gian Gentinetta will tell us about his master thesis at IBM, entitled ''The complexity of quantum support vector machines''. See below for the abstract. The talk will take place at 2pm in F31.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best,
Ladina
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Abstract:
Quantum support vector machines employ quantum circuits to define the kernel function. It has been shown that this approach offers a provable exponential speedup compared to any known classical algorithm for certain data sets. The training of such models corresponds to solving a convex optimization problem either via its primal or dual formulation. Due to the probabilistic nature of quantum mechanics, the training algorithms are affected by statistical uncertainty, which has a major impact on their complexity. We show that the dual problem can be solved in O(M^4.67/ε^2) quantum circuit evaluations, where M denotes the size of the data set and ε the solution accuracy. We prove under an empirically motivated assumption that the kernelized primal problem can alternatively be solved in O(min{M^2/ε^6, 1/ε^10}) evaluations by employing a generalization of a known classical algorithm called Pegasos. Accompanying empirical results demonstrate these analytical complexities to be essentially tight. In addition, we investigate a variational approximation to quantum support vector machines and show that their heuristic training achieves considerably better scaling in our experiments.
Hi all,
Tomorrow Martin Sandfuchs will tell us about his project with Ramona, entitled ''Computing key rates for device-independent quantum key distribution''. See below for the abstract. The talk will take place at 2pm in HIT F31.1 or on Zoom: https://ethz.zoom.us/j/362994444.
Best,
Ladina
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Abstract:
Quantum key distribution (QKD) aims to exploit the properties of quantum mechanics to produce a shared secret key between two distant users that is uncorrelated with the information held by an adversary. Device-independent QKD (DIQKD) tries to provide even stronger security guarantees by removing assumptions about how the devices operate. Unfortunately physical implementations of DIQKD pose significant experimental challenges and as a reaction a lot of theoretical work has gone into inventing improved protocols that can increase the tolerance to noise. A recent numerical method, developed by Peter Brown et al., has allowed for improved key rates in the asymptotic limit. In this presentation we demonstrate how this technique can be extended to the more realistic regime of finitely many key rounds. To do so we lower-bound the smooth min-entropy using the entropy accumulation theorem. We then build on previous DIQKD security proofs to propose a modified protocol which improves the threshold efficiency when performing DIQKD with lossy qubits.
Hi all,
Tomorrow Xavier Coiteux-Roy of USI Lugano will tell us about
"Quantum-resistant cryptography for Bennett-Maxwell demons". See below for
the abstract. The meeting will take place in HIT F13 and on zoom at the
usual address https://ethz.zoom.us/j/362994444.
Best,
Joe
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Title: Quantum-resistant cryptography for Bennett-Maxwell demons
Abstract: I will present how the second law of thermodynamics allows in
principle to achieve information-theoretically secure cryptographic
primitives such as secret-key establishment and oblivious transfer. While
idealized, our proposed protocols explore the limits of logically and
thermodynamically reversible computation and act as a focal point to
contrast the properties of information in different physical theories.
Hi all,
Tomorrow we'll hear from Alexander Schmidhuber, who did a semester project
with Esteban on "A covariant extension of the Page-Wootters mechanism to
spacetime". See the abstract below.
We can try a hybrid meeting for those who are at ETH and interested; I've
booked F31.1. The speaker will join us by zoom, so don't feel compelled to
join in person. The zoom link is the usual one,
https://ethz.zoom.us/j/362994444.
Best,
Joe
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Abstract:
Every observation in physics is made with respect to a frame of reference.
In any concrete scenario, this reference frame is constituted by a physical
system and thus subject to quantum phenomena such as entanglement and
superposition. A relativistic description of the laws of physics hence
needs to take into account such quantum reference frames. In this thesis,
we investigate a mechanism for temporal quantum reference frames developed
by Page and Wootters, and discuss its limitations. We show that two
a-priori different approaches to overcoming Kuchar's criticisms, developed
by Giovannetti, Lloyd & Maccone and Höhn, Smith & Lock, are equivalent.
Building upon this result, we construct a covariant extension of the
Page-Wootters mechanism to spacetime and derive the corresponding quantum
reference frame transformations for states and operators.
Dear all,
We are happy to invite you to a discussion group on philosophy and
foundations of physics involving members of the Theoretical Cosmology
and Quantum Information Theory groups. The group is open to students,
PhDs, Postdocs and Professors alike. We include a description of the
group and further details below, in case you are interested in
participating.
The motivation for this discussion group stems from the fact that a lot
of great physics, such as general relativity and quantum mechanics, has
been influenced by philosophical ideas. In turn, new physical and
mathematical insights have also sparked philosophical discussions. The
two disciplines are tightly related to each other and in many cases
there is no clear division between them.
We believe that discussions on philosophy and foundations deepen our
understanding of physics and mathematics. In our view, engaging in such
discussions can also guide our own research, sharpen our critical
thinking, and complement our computational, analytical and communication
skills. This view is also supported by the history of science, as great
insights have come from questioning the status quo, identifying biases,
prejudices or implicit assumptions. Furthermore, in recent years, there
has been a lot of interest and progress towards connecting ideas from
quantum information theory and gravity, which suggests the importance of
inter-disciplinary exchanges in making advances towards solving some of
the larger open problems in physics.
The spirit of these discussions is to promote exchanges between our
research groups in a flexible and open-minded manner. To get started, we
have compiled a list of topics that are potentially of interest to both
groups. This list of topics, along with a list of current participants
and potential guest speakers can be found at the following link. Any of
the participants are welcome to vote on existing topics, suggest further
topics and guest speakers. If you are interested in joining the group,
please request editing access on the google spreadsheet below, and also
include your details in the list of members, so that we can add you to
the mailing list for the group.
Once you have access to edit the spread sheet, you can vote on each of
the suggested topics, by clicking on the second tab, titled "List of
subjects and questions" and adding 1 to the corresponding entry in the
"vote" column. Please feel free to also add your topic and speaker
suggestions to the spreadsheet.
https://docs.google.com/spreadsheets/d/1FQ8-kvlKdu3mnVDjAP3FejzlXlCTotj5wlG…
In order to pick a suitable time for our first meeting, we have created
a doodle poll which is linked below. If you are interested in joining
the group, please fill out the poll as well. The first meeting would be
a good chance for all of us to get to know each other and decide on the
format of future meetings. If you would be joining, it would be great if
you could prepare to say a few sentences about yourself and your
research interests. We will aim to have the meeting in hybrid mode, with
the option of participating either in person or online. Once we have
finalised a date and time, we will inform you about the venue (if your
email is on the spreadsheet).
https://doodle.com/poll/5vybdcgufugcsxp2?utm_source=poll&utm_medium=link
We wish you a good end of the week and look forward to meeting and
getting to know you,
Best regards,
Fabio D'Ambrosio
Vilasini Venkatesh
Hi all,
Renato will deliver tomorrow's group seminar, on the topic of issues
surrounding the superposition of spacetime (if I understood
correctly). We will try a hybrid in-person / zoom event, starting at
2pm in HIT J52 and on zoom https://ethz.zoom.us/j/362994444.
Best,
Joe