QPL 2018 Program

All QPL talks will be held in room 1020 of the Kenneth C. Rowe Management building at 6100 University Avenue (building E260 on the campus map).

Saturday, June 2, 2018

6pm Informal gathering, Henry House Pub (basement), 1222 Barrington Street

Sunday, June 3, 2018

9:00–10:00 Invited lecture Debbie Leung Embezzlement-based nonlocal game that cannot be played optimally with finite amount of entanglement [abstract]

We first summarize recently found nonlocal games (with finite number of classical questions and answers) whose optimal winning probability can only be attained as a limit of strategies using arbitrarily high dimensional entangled states.

Then, we focus on one such game, an explicit three-player game with very few classical questions and answers. This game is based on the coherent state exchange game introduced in arXiv:0804.4118, which in turns is based on embezzlement of entanglement due to van Dam and Hayden. We discuss the main ideas behind each of these ingredients, and how they can be put together to obtain a quantitative tradeoff in the winning probability vs the dimension of the entangled state shared by the players.

Joint work with Zhengfeng Ji and Thomas Vidick, arXiv:1802.04926.

10:00–10:30 Ana Belén Sainz, Yelena Guryanova, Antonio Acín and Miguel Navascués Almost quantum correlations violate the no-restriction hypothesis [extended abstract]
10:30–11:00 Coffee break
11:00–11:30 Spencer Breiner, Amir Kalev and Carl Miller Three-party quantum self-testing with a proof by diagrams [paper]
11:30–12:00 Albert Atserias, Laura Mančinska, David Roberson, Robert Samal, Simone Severini and Antonios Varvitsiotis Quantum inspired relaxations of graph isomorphism [extended abstract]
12:00–12:30 Martino Lupini, Laura Mančinska and David Roberson Nonlocal games and quantum permutation groups [extended abstract]
12:30–2:00 Lunch break
2:00–2:30 Stefano Gogioso and Fabrizio Romano Genovese Quantum field theory in categorical quantum mechanics [paper]
2:30–3:00 Amar Hadzihasanovic, Giovanni de Felice and Kang Feng Ng A diagrammatic axiomatisation of fermionic quantum circuits [extended abstract]
3:00–3:30 Bart Jacobs Lower and upper conditioning in quantum Bayesian theory [paper]
3:30–4:00 Coffee break
4:00–4:30 Mathieu Huot and Sam Staton Categorical universal properties in quantum theory [paper]
4:30–5:00 Robert Furber Categorical equivalences from state-effect adjunctions [paper]
5:00–5:30 Chris Heunen and Martti Karvonen Limits in dagger categories [extended abstract]

Monday, June 4, 2018

9:00–10:30 Tutorial Teiko Heinosaari Compatibility of quantum measurements and channels
10:30–11:00 Coffee break
11:00–11:30 Thomas Galley and Lluis Masanes Impossibility of mixed-state purification in any alternative to the Born rule [extended abstract]
11:30–12:00 Matty Hoban and Ana Belén Sainz A channel-based framework for steering, non-locality and beyond [extended abstract]
12:00–12:30 Giulio Chiribella Agents, subsystems, and the conservation of information (extended abstract) [extended abstract]
12:30–2:00 Lunch break
2:00–2:20 Abraham Westerbaan, Bas Westerbaan and John van de Wetering Pure maps between Euclidean Jordan algebras [paper]
2:20–2:40 Cristhiano Duarte, Raphael Drumond and Roberto Oliveira Small violations of Bell inequalities for multipartite pure random states [extended abstract]
2:40–3:00 Andrew Fagan and Ross Duncan Optimising Clifford circuits with quantomatic [paper]
3:00–3:30 Kang Feng Ng and Quanlong Wang A universal completion of the ZX calculus [extended abstract]
3:30–4:00 Coffee break
4:00–4:30 Miriam Backens and Aleks Kissinger ZH: A complete graphical calculus for quantum computations involving classical non-linearity [paper]
4:30–5:00 Emmanuel Jeandel, Simon Perdrix and Renaud Vilmart Diagrammatic reasoning beyond Clifford+T quantum mechanics [extended abstract]
5:00–5:30 Renaud Vilmart A ZX-calculus with triangles for Toffoli-Hadamard, Clifford+T, and beyond [paper]
5:30–8:30 Poster reception. Atrium, Kenneth C. Rowe Management building

Tuesday, June 5, 2018

9:00–10:30 Tutorial Ciáran Lee Computation in a general physical setting [abstract]

The advent of quantum computing has challenged classical conceptions of which problems are efficiently solvable in our physical world. This raises the general question of what broad relationships exist between physical principles and computation. This tutorial will explore this question in the the operationally-defined framework of generalised probabilistic theories. To begin, the limits on computational power imposed by simple physical principles will be explored. After this, we shall investigate whether post-quantum interference is a resource for post-quantum computation. The tutorial will end with a conjecture asking whether quantum theory is optimal for computation in the landscape of generalised probabilistic theories satisfying a single physical principle.

10:30–11:00 Coffee break
11:00–11:30 John Selby and Jamie Sikora Cone programs and generalised probabilistic theories [extended abstract]
11:30–12:00 Tomáš Gonda, Ravi Kunjwal, David Schmid, Elie Wolfe and Ana Belén Sainz Almost quantum correlations are inconsistent with Specker’s principle [extended abstract]
12:00–12:30 Jonathan Richens, John Selby and Sabri Al-Safi Entanglement is necessary for emergent classicality in all physical theories [extended abstract]
12:30–2:00 Lunch break
2:00–2:30 Stan Gudder Contexts in convex effect algebras [extended abstract]
2:30–3:00 Nuriya Nurgalieva and Lídia Del Rio Inadequacy of modal logic in quantum settings [paper]
3:00–3:30 Dominique Unruh Quantum relational Hoare logic [extended abstract]
3:30–4:00 Coffee break
4:00–4:30 John Harding, Chris Heunen, Bert Lindenhovius and Mirko Navara Boolean subalgebras of orthoalgebras [extended abstract]
4:30–4:50 Benjamin Musto and Jamie Vicary Orthogonality for quantum Latin isometry squares [paper]
4:50–5:10 Stefano Gogioso Higher-order CPM constructions [paper]
5:10–5:30 Fabrizio Romano Genovese and Jelle Herold Executions in integral Petri nets are compact closed categories [paper]

Wednesday, June 6, 2018

(See also the program of MFPS 2018, held in parallel).

9:00–10:00 Invited lecture Dominic Horsman Surface code error correction and the ZX calculus [abstract]

In this talk I will give a gentle introduction to quantum surface codes, and to how the ZX calculus may be used as a high-level design and compilation language for them. I will show how using the ZX calculus simplifies an understanding of how the codes work, and in particular gives immediate access to the connection between 2D and 3D codes. Looking particularly at the operations of lattice surgery, I show how they form a direct model for the generators of the calculus in terms of 'splitting' and 'merging' operations. Interpreting the calculus in this operational way means coming to grips with probabilistic procedures, and I look at ways we can deal with this within ZX. Finally I show how having the calculus as a graphial language for error correction pays off in the compilation problem for quantum processes, and show how we get new operational procedures for protocols, including magic state distillation, from equational rewriting of the ZX diagrams.

10:00–10:30 Robin Cockett and Cole Comfort The category TOF [paper]
10:30–11:00 Coffee break
11:00–11:30 Andrew N. Glaudell, Neil J. Ross and Jacob M. Taylor Canonical forms for single-qutrit Clifford+T operators [paper]
11:30–12:00 Matthew Amy Towards large-scale functional verification of universal quantum circuits [paper]
12:00–12:30 Niklas Johansson and Jan-Åke Larsson Efficient classical simulation of some quantum algorithms [extended abstract]
12:30–2:00 Lunch break

Special session on quantum programming, joint with MFPS 2018

2:00–3:00 Invited lecture Neil J. Ross Proto-Quipper: A circuit description language for quantum computing [abstract]

Quipper is a functional programming language for quantum computation which has been used to implement various elaborate quantum algorithms. At the moment, Quipper is implemented as an embedded language, whose host language is Haskell. One of the disadvantages to Quipper being an embedded language is that the Haskell type system, while providing many type-safety properties, is not in general strong enough to ensure the full type-safety of quantum programs.

The Proto-Quipper language provides a foundation for the development of a stand-alone (i.e., non-embedded) version of Quipper. Like Quipper, Proto-Quipper acts as a circuit description language and provides the ability to treat circuits as data in order to manipulate them as a whole. However, Proto-Quipper is also designed to “enforce the physics”, in the sense that its type system would detect, at compile-time, programming errors that could lead to ill-formed or undefined circuits.

I will start my talk with a brief introduction to quantum computing and a discussion of the design principles behind Quipper. I will then present Proto-Quipper and discuss open problems.

3:00–3:30 Benoît Valiron On quantum and classical control [abstract]

One perspective on quantum algorithms is that they are classical algorithms having access to a special kind of memory with exotic properties. This perspective suggests that, even in the case of quantum algorithms, the control flow notions of sequencing, conditionals, loops, and recursion are entirely classical. There is however, another notion of control flow, that is itself quantum. The notion of quantum conditional expression is reasonably well-understood: the execution of the two expressions becomes itself a superposition of executions. The quantum counterpart of loops and recursion is however still unclear. In this talk, we argue that, under the right circumstances, a reasonable notion of quantum loops and recursion is possible. To this aim, we first propose a classical, typed, reversible language with lists and fixpoints. We then extend this language to the closed quantum domain (without measurements) by allowing linear combinations of terms and restricting fixpoints to structurally recursive fixpoints whose termination proofs match the proofs of convergence of sequences in infinite-dimensional Hilbert spaces. We additionally give an operational semantics for the quantum language in the spirit of algebraic lambda-calculi.

The talk will be based on arXiv:1804.00952.

3:30–4:00 Coffee break
4:00–4:30 Jennifer Paykin Preaching to the QWIRE: Verified semantics of quantum circuits [abstract]

Embedded quantum circuit languages like Quipper, LiQUi|⟩, and ProjectQ let programmers express high-level algorithms using host language libraries and features like recursion and data structures. But how can we verify the correctness of embedded quantum circuits without reasoning about the semantics of the entire host language? QWIRE (pronounced “choir”) is a quantum circuit language embedded in Coq, a dependently-typed programming language and interactive theorem prover. QWIRE both has the benefits of an embedded language and can be formally verified inside Coq itself. In this talk I will present the theory and semantics of QWIRE and show how to formally verify the correctness of quantum programs using QWIRE’s denotational semantics.

4:30–5:00 Vadym Kliuchnikov Tasks performed by programming languages for quantum computers and how Q# enables them [abstract]

We will discuss the requirements for programming languages for quantum computers and highlight the differences with programming languages for classical computers. Then we will see how these new requirements are addressed in Q#. This talk will also serve as an introduction to Q#.

5:00–5:30 Craig Gidney Optimizing quantum circuits with classical thinking [abstract]

Although quantum computing is now a decades-old field, there are still many low-hanging opportunities for improving the projected costs of quantum algorithms by orders of magnitude. For example, when designing an efficient quantum algorithm one can often identify nearly-classical subproblems. Efficient classical circuits for these subproblems translate into efficient quantum circuits for the original algorithm.

This talk will discuss a concrete example of the quantum-to-classical-and-back approach bearing fruit. I will show that preparing a particular type of superposition is equivalent to fitness proportionate selection (a classical task where one has a population of items with associated fitnesses and wishes to sample items with twice as much fitness twice as often). I will then explain an efficient classical algorithm for fitness proportionate selection, and translate it back into the quantum domain to produce the 'subprepare' oracle from arXiv:1805.03662, which prepares (and unprepares) superpositions with hardcoded coefficients 100x more efficiently than previous work.

5:30–10:00 Reception and conference dinner. University Club, 6259 Alumni Crescent (building C440 on the campus map)

Thursday, June 7, 2018

(See also the program of MFPS 2018, held in parallel).

9:00–10:00 Invited lecture Robert Spekkens Experimentally bounding deviations from quantum theory in the landscape of generalized probabilistic theories [abstract]

Many experiments in the field of quantum foundations seek to adjudicate between quantum theory and speculative alternatives to it. This requires one to analyze the experimental data in a manner that does not presume the correctness of the quantum formalism. The mathematical framework of generalized probabilistic theories (GPTs) provides a means of doing so. We present a scheme for determining what GPTs are consistent with a given set of experimental data. It proceeds by performing tomography on the preparations and measurements in a self-consistent manner, i.e., without presuming a prior characterization of either. We illustrate the scheme by analyzing experimental data for a large set of preparations and measurements on the polarization degree of freedom of a single photon. We find that the smallest and largest GPT state spaces consistent with our data are a pair of polytopes, each approximating the shape of the Bloch Sphere and having a volume ratio of 0.977 ± 0.001, which provides a quantitative bound on the scope for deviations from quantum theory. We also demonstrate how our scheme can be used to bound the extent to which nature might be more nonlocal than quantum theory predicts, as well as the extent to which it might be more or less contextual. Specifically, we find that the maximal violation of the CHSH inequality can be at most 1.3% ± 0.1 greater than the quantum prediction, and the maximal violation of a particular noncontextuality inequality cannot differ from the quantum prediction by more than this factor on either side.

10:00–10:30 Ravi Kunjwal Beyond the CSW framework: a hypergraph-theoretic framework for Spekkens contextuality [extended abstract]
10:30–11:00 Coffee break
11:00–11:30 David Schmid and Robert Spekkens Contextual advantage for state discrimination [extended abstract]
11:30–12:00 Martti Karvonen Categories of empirical models [paper]
12:00–12:30 Giovanni Carù Towards a cohomology invariant for non-locality and contextuality [extended abstract]
12:30–2:00 Lunch break
2:00–2:20 Robert Rand, Jennifer Paykin, Dong-Ho Lee and Steve Zdancewic ReQWIRE: Reasoning about reversible quantum circuits [paper]
2:20–2:40 Sean Tull A categorical reconstruction of quantum theory [extended abstract]
2:40–3:00 John van de Wetering Sequential measurement characterises quantum theory [extended abstract]
3:00–3:30 John Selby, Carlo Maria Scandolo and Bob Coecke Reconstructing quantum theory from diagrammatic postulates [extended abstract]
3:30–4:00 Coffee break
4:00–4:30 Stefano Gogioso, Dan Marsden and Bob Coecke Symmetric monoidal structure with local character is a property [paper]
4:30–5:00 Bert Lindenhovius, Michael Mislove and Vladimir Zamdzhiev Enriching a linear/non-linear lambda calculus: a programming language for string diagrams [extended abstract]
5:00–5:30 Samson Abramsky, Rui Soares Barbosa, Nadish de Silva and Octavio Zapata The quantum monad: towards quantum finite model theory [extended abstract]