Cedric Beny
Information Flow in the Heisenberg Picture
We propose to characterize the information transmitted by a quantum channel in terms of the observables whose statistical information can be recovered after action of the channel, for arbitrary input state. When the observables considered are sharp this information can be corrected in the sense of the new theory of operator algebra quantum error correction. We use this concept to understand how the information carried by a channel is related to that carried by the complementary channel. This yields new insights on the process of decoherence and on the quantum theory of measurement.

Erwann Bocquillon
Single photon source on a breadboard
In quantum information, one can prove that a secure quantum cryptography channel based on photon key distribution requires reliable single photon sources. If not, a potential eavesdropper may be able to get information using the extra photons. Current sources are based on either attenuated laser beams, which may produce randomly 2 or even more photons at a time following a poissonian statistics, or either based on two level-systems providing single photon sources often requiring cooling or complex set-ups.
The goal of our experiment is to provide an easy, robust and compact single photon source using nonlinear optics (parametric down-conversion). We want to study its statistics and compare it to other photon sources. We could use this heralded single photon source to create a quantum communication channel.

Cyril Branciard
Distributed phase reference schemes for QKD : Explicit attacks and security considerations.
Distributed phase reference schemes are a new class of protocols for Quantum Key Distribution, in which the quantum signals have overall phase-relationships to each other. This is expected to protect against some loss-related attacks. However, proving the full security of these schemes is a new challenge for theorists, as one can no longer identify individual signals (such as qubits in BB84, for instance), and so the security proof techniques do not apply directly.

In this talk I will present two such protocols (the Differential Phase Shift and the Coherent One Way protocols). Their "unconditionnal security" has not been proven yet, but I will present some specific attacks on these schemes, which give us upper bounds for the security, as well as a "feeling" on how these schemes should perform.

Anne Broadbent
Anonymous quantum communication
We present an information-theoretically secure protocol for the
transmission of a quantum state between an anonymous sender and an
anonymous receiver. The anonymity is perfect and so is the privacy
of the message. No assumption is made on the number of honest
participants and this leads to a protocol in which a single participant can cause an abort. Unless the receiver is corrupt, the quantum state is never destroyed; thus the state is either transferred to the receiver or it remains in the hands of the sender.

Yaron Bromberg
Coherent Control with Time-Energy entangled photons
Most of the experimental advances in coherent quantum control in recent years have involved ultrashort pulses and pulse shaping techniques. These pulses have been an excellent source of coherent light with precise phase relationship between the various frequency components. In several recent works we have investigated the possibility of using broadband nonclassical light, generated by down-conversion of narrow-band lasers, for coherent control.

We demonstrated that pulse shaping techniques can be used in the single-photon limit, when the light is composed of individual time-energy entangled photons. We could shape the two-photon correlation function, which is as close as one can get to ‘shaping of individual photons’. Using polarization pulse-shaping techniques we also controlled the quantum interference of polarization entangled photons. By controlling both phase and polarization of the photon-pairs, we were able to tailor the Hong-Ou-Mandel interference pattern, and generate all four polarization Bell-states.

We believe that the combination of quantum control techniques with quantum optics could add an important ingredient to the toolbox of quantum information and computing.

Félix Bussières
A New Protocol for Loss-Tolerant Quantum Coin Tossing
Quantum coin tossing is a cryptographic task in which two parties, Alice and Bob, wish to generate a shared random bit but do not necessarily trust each other. This task is completely impossible to realize with classical asynchronous communication but becomes at least partially feasible when quantum communication is also available. The best quantum protocol known so far, due to Ambainis, uses qutrits and is near optimal in the sense that either party can bias the outcome with at most a 75% probability of success. However, when the transmission of the link is below 50%, Ambainis'  protocol can be easily broken by a cheating Bob. This problem arises whenever there exists a conclusive measurement allowing Bob to obtain with certainty, although with a probability less than one, relevant information about the state sent by Alice. In this talk, we will present a new protocol for quantum coin tossing that does not suffer from this weakness and, as a consequence, is loss-tolerant. We discuss possible attacks and argue that the protocol is secure. Technologically, the implementation of this protocol is no more difficult than implementing entangled quantum key distribution with qubits. This is joint work with Guido Berlin, Gilles Brassard and Nicolas Godbout.

Filippo Caruso
Degradability of Bosonic Gaussian Channels
The notion of weak-degradability of quantum channels is introduced by generalizing the degradability definition given by Devetak and Shor.  Exploiting the unitary equivalence with beam-splitter/amplifier channels we then prove that a large class of one-mode Bosonic Gaussian channels are either weakly degradable or anti-degradable. In the latter case this implies that their quantum capacity Q is null. In the former case instead, this allows us to establish the additivity of the coherent information  for those maps which admit unitary representation with single-mode pure environment.

Andrea Casaccino
Subsystem Quantum Error Correcting Codes
The essential insight of quantum error correction was that quantum information can be protected by suitably encoding this quantum information across multiple independently erred quantum systems. Recently it was realized that, since the most general method for encoding quantum information is to encode it into a subsystem, there exists a novel form of quantum error correction beyond the traditional quantum error correcting subspace codes. These new quantum error correcting subsystem codes differ from subspace codes in that their quantum correcting routines can be considerably simpler than related subspace codes. Here we present a class of quantum error correcting subsystem codes constructed from two classical linear codes. These codes are the subsystem versions of the quantum error correcting subspace codes which are generalizations of Shor’s original quantum error correcting subspace codes. For every Shor-type code, the codes we present give a considerable savings in the number of stabilizer measurements needed in their error recovery routines.

Donny Cheung
Classical Post-processing for Low-Depth Phase Estimation Circuits
Traditionally, we use the quantum Fourier transform circuit (QFT) in order to perform quantum phase estimation, which has a number of useful applications.  The QFT circuit for a binary field generally consists controlled-rotation gates which, when removed, yields the lower-depth approximate QFT circuit.  It is known that a logarithmic-depth approximate QFT circuit is sufficient to perform phase estimation with a degree of accuracy negligibly lower than that of the full QFT.  However, when the depth of the AQFT circuit becomes even lower, the phase estimation procedure no longer produces results that are immediately correlated to the desired phase.  In this talk, I will explore the possibility of retrieving this information with classical analysis and with computer post-processing of the measured results of a low-depth AQFT circuit in a phase estimation algorithm.

Niel de Beaudrap
An introduction to one-way patterns
The one-way measurement model is a model of quantum computation which is intriguing for its' potential as a means of implementing quantum computers, but also for theoretical purposes for the different way in which it allows quantum operations to be described. Instead of a sequence of unitary gates on an array of ``wires'', operations are described in terms of emph{patterns}, consisting of a graph of entanglement relations on a set of qubits, together with a collection of measurement angles for these qubits (except possibly for a subset which will support a final quantum state). In this introductory talk, I describe the relationship between patterns in the one-way measurement model to quantum circuits, and explore patterns which represent unitary operations but which emph{don't} have direct analogues in the circuit model.

Frédéric Dupuis
Approximate quantum encryption and entropic security
An approximate quantum encryption scheme uses a private key to encrypt a quantum state while leaking only a very small (though non-zero) amount of information to the adversary. Previous work has shown that while we need 2n bits of key to encrypt n qubits exactly, we can get away with only n bits in the approximate case, provided that we know that the state to be encrypted is not entangled with something that the adversary already has in his possession. In this talk I will show a generalization of this result: approximate quantum encryption requires roughly n-t bits of key, where t is a lower bound on the conditional min-entropy of the state to be encrypted given the adversary's prior knowledge. Along the way, I will introduce a quantum version of entropic security and show how the approximate quantum encryption scheme fits within this framework. This is joint work with Simon-Pierre Desrosiers.

Agnes Ferenczi
Calibration Attack and Defense in Continuous Variable Quantum Key Distribution
We have found new attacks against Continuous Variable Quantum Key
Distribution based on the accessibility of the phase reference beam by
the adversary. We then give easy countermeasures to this attack and
prove their security.

Chris Ferrie
Quantum mechanics in phase space
Many authors have proposed what are known as "phase-space" or "classical" representations of quantum mechanics.  A unifying framework is given which illustrates the relationship among these various theories.  Examples relevant to quantum computing will be given.

Chi-Hang Fred Fung
Practical quantum-key-distribution systems with detector efficiency mismatch: attacks and secret key rates
Imperfections in devices are inevitable in practice.  In this talk, we focus on the imperfection of QKD systems in the detectors, namely that the efficiencies of the detectors are not completely identical.  We show some practical attacks that specifically exploit this efficiency mismatch and demonstrate how Eve may obtain some information on the final key if Alice and Bob are unaware of the attack.  Also, we discuss the upper and lower bounds on the secret key rates both with and without the assumption of the efficiency mismatch. (20 min)

Sébastien Gambs
On connections between machine learning and quantum information processing
Quantum Information Processing (QIP) is concerned with the implications of quantum mechanics for information processing purposes whereas Machine Learning (ML) is the field that studies techniques to give to machine the ability to learn from past experience. Typical tasks in ML include the ability to predict the class (classification) or some unobserved characteristic (regression) of an object based on some observations in supervised learning, or the ability to find some structure hidden within data (clustering, dimensionality reduction or density estimation) in unsupervised learning.

ML and QIP may seem a priori to have little to do with one another but nevertheless they have already met several times in a fruitful manner. The purpose of this talk is to give an overview of some of these past and recent encounters with the hope of encouraging
further collaboration between these two domains. Examples of encounters between ML and QIP include the comparison of the quantum and classical settings in computational learning theory, the definition of quantum analogues of ML algorithms such as neural networks, the application of the machine learning paradigm to quantum states and the quantization of clustering algorithms. These and other examples will be discussed during the presentation.

Hauke Haseler
Verifying Entanglement in Quantum Optical Systems
We present an entanglement verification method for systems with underlying
qubit-mode structure, which does not require full knowledge of the bi-partite density
matrix. It is applied to a quantum key distribution experiment with coherent signal
states and one of two different detection schemes: For heterodyne detection, it is
possible to detect entanglement even in the presence of loss and noise whereas for
Stokes operator measurements, entanglement verification fails.

Richard Low
Toward a quantum Fourier transform on SU(2).
Almost all known superpolynomial quantum speedups over classical algorithms have used the quantum Fourier transform (QFT). Most known applications of the QFT make use of the QFT over abelian groups, including Shor’s well known factoring algorithm [1]. However, the QFT can be generalised to act on non-abelian groups allowing different applications. For example, Kuperberg solves the dihedral hidden subgroup problem in subexponential time using the QFT on the dihedral group. The aim of this research is to construct an efficient QFT on SU(2). Most of the progress in constructing QFTs has come from applying ideas from classical algorithms such as subgroup adapted bases. For example, Moore et al.  have applied classical ideas from e.g.  to build non-abelian QFTs. Applying these ideas to infinite groups such as SU(2) requires new tools. The function must be sampled or discretised in a way so as to minimise the error. I will present some ideas based on classical algorithms which may lead to a QFT over the group SU(2) for band limited functions. There are problems with making these algorithms unitary that must be addressed and efficient methods for calculating coefficients (cf. the controlled phase gates in the abelian case) must be found.

Mark Mercer
Lower bounds for Generalized Quantum Finite Automata
For most variations of Quantum finite automata (QFA), it is an open question to characterize the language recognition power of these machines. We extend several techniques used to obtain lower bounds on Kondacs and Watrous' 1-way Quantum Finite Automata to the case of Nayak's Generalized Quantum Finite Automata (GQFA). A consequence of these results is that the class of languages recognized by GQFAs is not closed under union.

Geir Ove Myhr
Symmetric extendibility of quantum states
Imagine that Alice and Bob share a quantum state, from which they want to distill something useful like entanglement or secret key. For this they need to communicate classically and they want to do this by one way communication from Alice to Bob. For some states, it might happen that the state is a part of a tripartite state shared with Charlie, which is invariant if Bob's and Charlie's systems are switched. Such a state is called a symmetric extension, and if it exists Alice and Bob have no chance of distilling key or entanglement by one way communication. I will present some results characterizing which quantum states have symmetric extension.

Carlos Perez
Quantum Cellular Automata Applications
TBA

Bill Rosgen
Multiplicativity and Strong Multiplicativity of Norms on Transformations
Proving the additivity of the classical capacity of quantum channels is a major open problem in quantum information.  This problem is related to the multiplicativity of certain norms with respect to the tensor product.  These problems are introduced and some approached to resolving them are discussed.  Several special cases that have been solved are also mentioned. (20 min)

Colm Ryan
Purifying qubits in NMR quantum information processing
Any implementation of  a quantum computer will require the ability to reset qubits to a pure input state, both to start the computation and more importantly to implement fault-tolerant operations.  Even if we cannot reset to a perfectly pure state, heat-bath algorithmic cooling provides a method of purifying mixed states.  By combining the ability to pump entropy out of the system through a controllable interaction with a heat bath and coherent control of the qubits, we are able to cool a subset of the qubits far below the heat bath temperature.  Here we show an implementation of this cooling in a solid state NMR quantum information processor which offers high fidelity control of the qubit system and controllable access to a heat bath.   We demonstrate an implementation of multiple rounds of heat-bath algorithmic cooling on three qubits and discuss the improvements in control techniques which have allowed us to show the purification of a single qubit to one and a half times the heat bath polarization.

Lana Sheridan
Degradation of a quantum directional reference frame
In this study, we are interested in the practical question of how many times a quantum directional reference frame (i.e., a spin-J system) can be used to perform a certain task with a given probability of success, under the assumption that the quantum directional reference frame evolves under a map that is covariant under rotations in SU(2). Our main theorem restricts the form of the state of the quantum reference frame as a function of how many times the covariant map was applied to it. Our results are a generalization of the paper of Bartlett el al. on the degradation of reference frames, and can be used to analyze certain types of interactions on a spin-J system.

Joshua Slater
Towards the Production of Entangled Photon Pairs in Optical Fiber via Four-Wave Mixing
Previous experiments on the production of entangled photon pairs directly in optical fiber via four-wave mixing (FWM) have used a single pump laser and produced signal and idler photons with similar wavelengths. We will present the first results of our investigation into the production of widely separated entangled photon pairs via FWM in optical fiber using multiple pump lasers also at widely separated wavelengths. This source will have important applications in quantum cryptography and computation. As fiber optic and free space quantum communication networks require photons at different wavelengths (1550 nm and around 800 respectively) this source will make hybrid quantum cryptography networks achievable and could also be used as a heralded optical fiber source of single photons.

Devin Smith
A Polarization Entangled Photon Source Based on a Modified Sagnac Interferometer
A new source of polarization entangled photons is presented based on a bidirectionally pumped spontaneous parametric down-conversion crystal in the loop of a Sagnac interferometer. The source is pumped with a pulsed Ti:SA laser, allowing for high photon pair production rates and the potential for multi-photon experiments. Implementation, detection, and preliminary experimental results will be discussed.

Douglas Stebila
Quantum Key Distribution Networks
Current physical implementations of quantum key distribution (QKD) require communicating parties to be close together.  We will explore methods for allowing parties separated by long distances to communicate by combining many QKD links in a network and discuss the resulting security properties.

Yasaman Soudagar
Cluster State Quantum Computing in Optical fibres
In this presentation I will briefly explain the cluster state model of quantum computing. Then will talk about a scheme that uses polarization and time-bin degrees of freedom of photons in optical fibres for the optical realization of this model. We are currently working on the implementation of this scheme in our lab.

Anya Tafliovich
A formal approach to QC
A formal analysis of quantum algorithms and quantum protocols: correctness, probabilistic analysis, time, space, and communication complexity, distributed systems, non-locality games.

Man-Hong Yung
Quantum Network Engineering
I shall describe how to engineer quantum spin networks for perfect state transfer, entanglement generation and quantum computation.

Lucy Liuxuan Zhang
Learning about topological quantum memory
I will introduce Kitaev's suface codes as a block quantum error-correcting code.  Recovery procedures will be described in the case of imperfect syndrome measurements.  More might be covered if time permits.