### Program launches

CIFAR launches the program in Quantum Information Processing amidst widespread

Founded | 2002 |
---|---|

Renewal dates | 2007, 2012 |

Members | 34 |

Disciplines | |

Computer science, including quantum computing and theory of computation; quantum, condensed matter, mathematical and atomic physics; optics; electronic and information engineering; applied mathematics
CIFAR Contact
Lara O’Donnell, Senior Director, Research |

Today’s digital world is binary: a switch is either on or off, one or zero. But in the subatomic world of quantum physics, different rules hold sway. Some particles can exist in two or more states simultaneously. Others can react instantly to changes taking place miles away. These properties could allow us to build computers entirely unlike those we have today. Quantum computation could allow us to break unbreakable codes, model impossibly complex phenomena and solve problems previously thought to be unsolvable.

Quantum information science exists at the interface between computer science and quantum physics. For this reason, it is inherently interdisciplinary, requiring input from experts in many different fields. CIFAR brings together 35 leading researchers from mathematics, computer science, cryptography, theoretical physics, experimental physics, chemistry, engineering and other relevant disciplines. Together, these researchers aim to harness the power of quantum mechanics and create exponentially more powerful computers.

Quantum computing could affect society on a scale similar to that of the digital computer revolution. When researchers solve the theoretical and practical problems, quantum computing promises to vastly increase the computational speed, security and power available to us.

In 1994, mathematician Peter Shor published a famous algorithm about calculating the prime factors of very large numbers. This is a task that would take classical computers millions of years, but Shor’s algorithm showed that a quantum computer could do it in minutes. Not only did this provide a concrete example of a problem that only quantum computers could solve, it also had serious implications for the world of computer security. Many common cryptography algorithms — the technology used to keep banking transactions and other sensitive information secret — rely on the fact that factoring large numbers is something that cannot quickly be done by classical computers. If a quantum computer could be built, it could break almost any existing security code and allow for more secure cryptography.

In addition to cryptography, quantum computation could solve difficult optimization problems — that is, selecting the best solution out of a large set of possible answers. Examples include finding a drug molecule that would bind to a particular target in the human body, or choosing the best price at which to sell a product in a crowded and complex market. If quantum computers can solve those problems more quickly than classical computers, they could have huge implications for banking, medicine, defence and many other fields.

Researchers in the program are exploring fundamental questions about what exactly a quantum computer will be capable of, and how one can be built. In many cases they have done important groundwork in the field. Program Director Raymond Laflamme, for instance, laid down the fundamental mathematical work behind the quantum error-correcting codes that will be necessary for a working quantum computer. Advisor David Cory was the first to experimentally demonstrate that nuclear magnetic resonance technology could be used for quantum computation. Senior Fellow Gilles Brassard is the co-inventor of the first quantum cryptography algorithm. The program’s experimentalists work closely with theorists to create systems in which quantum behaviour can be controlled and exploited. In these systems, qubits consisting of photons or other quantum particles are being manipulated using the quantum phenomena of superposition and entanglement in order to store, retrieve and transmit information. CIFAR’s quantum information science program is organized around three major themes:

- Where does the power of quantum computation come from?

Even if the final form of quantum computers remains undecided, mathematicians and theoretical physicists can still design quantum algorithms and compare their performance with conventional computer programs. These researchers aim to find problems for which quantum computation offers a real advantage. For example, a team of CIFAR researchers led by Fellow David Poulin recently showed that quantum computations could be used to simulate the behaviour of atoms in molecules more accurately than conventional computer models. Advanced quantum models could be used to design new drugs or high-performance materials.

- How can we control quantum systems?

In order to get qubits to show quantum behaviour, they need to be isolated from heat or any other external source of energy. This is one of the major challenges to building a working quantum computer. Generally, quantum computing devices are built using materials that have been super-cooled to temperatures near absolute zero. Other tools of the trade include superconductors, lasers and advanced sensors tuned to measure quantum properties. For example, a team led by Associate Fellow Amir Yacoby recently proposed a way to use tiny magnetic particles to amplify the nuclear spin of qubits so they can be more easily measured. The goal is to be able to reliably write information to qubits by changing their properties, and later to read this information back. Laflamme has built a working model containing a dozen qubits. An international team led by Fellow Thomas Jennewein has created a system capable of transmitting quantum information over hundreds of kilometers. Such systems, if interlinked through a network of satellite and ground stations, could serve as the basis of a ‘quantum internet’. Jennewein’s team has also demonstrated a system that links three widely separated qubits through quantum entanglement

- What would quantum cryptography look like?

Quantum computers could easily break most modern forms of computer cryptography. But they could also create new forms of cryptography thanks to the principle of entanglement. If a sender and receiver each have one of an entangled pair of qubits, they could send information between them in a highly secure way. Even if an interloper did try to take a peek at the information, the mere act of observation would affect the pairs and send an alert that the message had been compromised. This system, known as quantum key distribution, is being tested experimentally by CIFAR researchers like Jennewein. His Quantum EncrYption and Science Satellite (QEYSS) project aims to demonstrate the generation of encryption keys through the creation of quantum links between ground and space.

Knill, E., Laflamme, R., Milburn, G.J. (2001) A scheme for efficient quantum computation with linear optics. *Nature* 409: 46-52 Negrevergne, C., Mahesh, T.S., Ryan, C.A., Ditty, M., Cyr-Racine, F., Power, W., Boulant, N., Havel, T., Cory, D.G., Laflamme, R. (2006) Benchmarking quantum control methods on a 12-qubit system. *Physical Review Letters*, 96: 170501 and also *Virtual Journal of Nanoscale Science & Technology* – May 15, 2006 Volume 13, Issue 19. arXiv:quant-ph/0412076 L. A. Rozema et al., “Quantum Data Compression of a Qubit Ensemble,” Physical Review Letters 113, 16 (2014) doi: http://dx.doi.org/10.1103/PhysRevLett.113.160504. J. Zhang et al., “Digital quantum simulation of the statistical mechanics of a frustrated magnet,” *Nature Communications* 3, 880 (2012) doi:10.1038/ncomms1860.

Contact the program’s senior director, Lara O’Donnell at lara.odonnell@cifar.ca

David Poulin’s research focuses primarily on finding efficient methods to protect quantum information. This includes the design of high-performance quantum error correcting codes and the search for innovative fault-tolerant techniques.…

Aephraim Steinberg’s interests lie in fundamental quantum-mechanical phenomena and the control and characterization of the quantum states of systems ranging from laser-cooled atoms to individual photons. His experimental program is…

Senior Fellow

University of Waterloo, Perimeter Institute for Theoretical Physics

Canada

Advisory Committee Chair

University of Waterloo Perimeter Institute for Theoretical Physics

Canada

2002
### Program launches

CIFAR launches the program in Quantum Information Processing amidst widespread excitement about the possibilities in this young, promising area of research. Many questions remain unanswered about the nature of quantum information, and experimentalists are in hot pursuit of technologies that can encode information in quantum bits. The experts say they need the best minds and support from CIFAR to pursue risky, long-term research directions — with theorists and experimentalists collaborating together — to make progress in a field that could change our world.

2003
### Quantum walk speeds up algorithm

CIFAR Senior Fellow **Richard Cleve** (University of Waterloo) and collaborators produce an example of a quantum walk — a quantum analog of a classical algorithm tool called a random walk — that greatly reduces the amount of time needed to solve a certain type of problem. This proves in principle that classical methods take exponentially more time than quantum approaches to solve certain types of problems.

2003
### Quantum entanglement improves remote communication

CIFAR Senior Fellow **Gilles Brassard**, Fellow **Alain Tapp** (both University of Montreal) and others establish a fundamental relationship between the enigmatic structure of quantum theory and the concrete achievability of communication tasks. They show that even though quantum entanglement cannot be used to transmit information between remote parties, it can reduce the amount of communication needed for computing tasks. They prove it is possible for two separated parties to compute arbitrary functions of their inputs, with only a trivial amount of communication.

2004
### Geometry proves useful for studying quantum entanglement

CIFAR Fellow **Patrick Hayden** (McGill University) and colleagues participate in a “grand unification” of concepts in quantum information theory. Hayden finds that something called the random subspace method, which originates geometry, is useful for studying quantum entanglement. He and collaborators identify a master protocol from which many others can be immediately inferred. The research could help with communication.

2004
### A new way to study light and matter

CIFAR Fellow **Alexandre Blais** (Université de Sherbrooke) and others propose an architecture for quantum computing using quantum electrodynamics for superconducting electrical circuits. The system provides a fundamental way to study the interaction of light and matter. With these superconductors, circuits can be fabricated to behave like atoms (superconducting qubits) or as a cavity does for an atom.

2005
### Nuclear magnetic resonance quantum computing advances

CIFAR Program Director **Raymond Laflamme**’s University of Waterloo laboratory makes significant progress in the area of nuclear magnetic resonance (NMR) quantum computing, which uses the spin states of molecules as qubits, or quantum bits. For example, they demonstrate new algorithmic techniques to cool systems to the low temperatures needed for success. In addition, they demonstrate many forms of quantum control and quantum error correction in medium-sized molecules.

2006
### Proving what quantum computers can’t do

CIFAR Fellow **Andris Ambainis** (University of Latvia) introduces a new methodology for proving the limits of what quantum computers can do, meaning which problems are too complex even for a quantum computer to solve. This becomes an important and widely applicable tool, as most known quantum algorithms can be cast in this model and these limits, or lower bounds, can be used to provide evidence that algorithms are optimal.

2006
### The trouble with spin chains determined

CIFAR Senior Fellow **Daniel Gottesman** (Perimeter Institute for Theoretical Physics), with collaborators from Caltech Institute for Quantum Information, identifies that a one-dimensional spin chain with short-range interactions can be as hard to simulate as the most general quantum problem in any dimension. This breakthrough has implications for many-body quantum physics, being that one-dimensional quantum spin-glasses are possible.

2006
### Secret verification proved possible for quantum information

CIFAR Fellow **John Watrous** (University of Waterloo) single-handedly resolves an outstanding question in theoretical computer science related to security. He studies “zero-knowledge” proof systems, which are protocols in which one party — the prover — tries to convince another — the verifier — that a fact is true without telling them the fact itself. A common example involves a girl named Peggy trying to prove to her friend Victor that she knows the secret word to open a door, without telling Victor the word. Researchers thought this concept couldn’t be applied to quantum information as it is in classical information, but Watrous shows that the concept carries over into the quantum realm. He develops a technique that allows several protocols to remain zero-knowledge against quantum attacks.

2007
### Quantum algorithm speeds up search

CIFAR Fellow **Ashwin Nayak** (University of Waterloo) and collaborators design a new quantum algorithm that converts any random walk into a quantum one and uses it to speed up search algorithms. Advantages of this algorithm include conceptual and technical simplicity, improved efficiency and demystification of the role of quantum walks in search algorithms.

2007
### Quantum walk algorithm plays match

CIFAR Fellow **Andris Ambainis** (University of Waterloo) discovers a quantum walk-based algorithm for a problem called “element distinctness.” Given a list of numbers, the algorithm must determine whether or not it contains two that are equal. This algorithm is applicable to the design of further quantum algorithms for some graph problems and matrix identity problems.

2008
### Quantum security faults found

CIFAR Fellow **Hoi-Kwong Lo** (University of Toronto) and collaborators demonstrate how the imperfect implementation of some commercial implementations of quantum key distribution (QKD) systems could be hacked. This breakthrough supports subsequent development of a method to certify QKD systems.

2008
### Quantum cryptography deployed in Waterloo

CIFAR Fellow **Gregor Weihs** (Universität Innsbruck), Program Director **Raymond Laflamme** (University of Waterloo) and collaborators deploy a free space cryptography system using a source of entangled photons that is free from hacking flaws. This system is deployed in Waterloo, making it the first Canadian free space QKD system and a founding block for the development of quantum technologies in Canada.

2009
### Quantum computing helps classical computing

CIFAR Fellow **John Watrous** (University of Waterloo) and collaborators show that quantum computation can yield new results in classical computer science, marking a major breakthrough in the field. They use ideas from learning theory to produce a parallel algorithm for a type of optimization problem known as semidefinite programs. Their results deepen the connection between quantum algorithms and semidefinite programs.

2009
### Superconducting quantum processor built

CIFAR Global Scholar **Jay Gambetta** (University of Waterloo), Fellow **Alexandre Blais** (Université de Sherbrooke) and a team of physicists from Yale University create a two-qubit superconducting quantum processor — a step toward building a quantum computer. They also use the two-qubit superconducting chip to successfully run elementary algorithms, such as a simple search, demonstrating quantum information processing with a solid-state device for the first time. Their groundbreaking research is described in Nature.

2009
### Quantum algorithm simulations

CIFAR fellows make it easier to invent and discover new algorithms by unifying different kinds of quantum algorithms. **Richard Cleve**, **Michele Mosca** (both University of Waterloo), **Daniel Gottesman** (Perimeter Institute for Theoretical Physics), **Barry Sanders** (University of Calgary) and collaborators show that certain quantum algorithms can be used to simulate others, effectively translating non-standard algorithms into “standard” ones with little or no slowdown.

2010
### Quantum devices can handle faults

CIFAR Senior Fellow **Michele Mosca** (University of Waterloo) and others shows that even imperfect quantum devices can be good enough to continue operating if some of their components fail — an important step towards practical implementations of quantum computing.

2010
### Quantum law confirmed

CIFAR fellows **Raymond Laflamme**, **Thomas Jennewein** (both University of Waterloo) and **Gregor Weihs** (Universität Innsbruck) use optics to perform experiments that test contextuality in quantum ensembles, a considerable advancement in the field. Their discovery rules out the existence of higher-order interferences experimentally and thereby confirms an axiom in quantum physics known as Born's rule, which determines the probability of a measurement on a quantum system yielding a certain result.

2010
### Quantum privacy protocol developed

CIFAR Senior Fellow **Gilles Brassard** (Université de Montréal), motivated by interactions with other fellows including Global Scholar **Anne Broadbent** (University of Ottawa) and fellows **Claude Crépeau** (McGill University) and **Alain Tapp** (Université de Montréal), develops quantum protocols for oblivious transfer and “blind” quantum computation, where a user can arrange for a quantum server to carry out a computation while maintaining the user’s privacy about the nature of the computation. This advances our understanding of security and privacy in a quantum world.

2011
### New cryptographic protocols for secure communication

Fellow **Gilles Brassard** (University of Montreal) and Scholar **Peter Høyer** (University of Calgary) and their collaborators demonstrate a significant milestone in post-quantum cryptography — the study of cryptosystems. They discover new cryptographic protocols that make possible the secure exchange of private information between two conventional computers, even if a would-be eavesdropper has the powerful advantage of quantum computing.

2011
### Three spin states manipulated

CIFAR Fellow **Andrew Sachrajda** (National Research Council) and Scholar **Michel Pioro-Ladrière** (Université de Sherbrooke) are part of a team that achieve a breakthrough in quantum computing. For the first time, they manipulate the spin states of three interacting electrons. The result is a significant leap forward in the effort to develop semiconductor quantum circuits, in which electron spins serve as quantum bits, or qubits. Spin is an intrinsic magnetic property of electrons, and its direction can be either ‘up’ or ‘down.’ Learning to control and manipulate spin holds the potential to advance both fundamental science and new applications.

2011
### Uncertainty principle skirted

Performing a “new take” on an iconic physics experiment, Fellow **Aephraim Steinberg** (University of Toronto), Global Scholar **Krister Shalm** (University of Waterloo) and other collaborators skirt a challenging fundamental rule of quantum mechanics: that any attempt to directly observe or measure a quantum system actually alters it. They demonstrate for the first time a way to successfully trace the pathways travelled by photons – quantum particles of light – through two slits and on to a screen without disrupting their behaviour. Steinberg and his collaborators get around this longstanding problem using “weak measurement,” a technique that obtains only very little information about each particle. Because the measurement is so weak, the particle’s behaviour is not significantly altered. By repeating the weak measurements many times on different particles, the team is able to plot the average path the particles travelled. These results demonstrate that a quantum system can behave like a wave and a particle at the same time.

2012
### A quantum satellite proposed

CIFAR Fellow **Thomas Jennewein** (University of Waterloo) proposes a quantum satellite, dubbed QEYSSat, to demonstrate the capacity for global quantum communication and enable scientists to test the fundamental properties of quantum mechanics on an unprecedented scale. The proposal follows an experiment by an international research team including Jennewein that achieved a record-breaking quantum teleportation distance of 143 kilometres in 2012, transferring quantum information between two of the Canary Islands. The experiment suggests that a satellite-based quantum communications system is practical. The Canadian Space Agency supports technical studies and explores a prospective mission.

2012
### Topological quantum computation reduces error rate

CIFAR Fellow **Robert Raussendorf** (University of British Columbia) demonstrates that topological error correction is valid. Topological error correction, which combines topological quantum computation with quantum error correction, is a promising approach for ensuring that a quantum computer can solve complex problems even if there are faults in its operation. Raussendorf and colleagues show how this method can protect computations against an error on a quantum bit and reduce the overall error rate significantly.

2012
### A step toward quantum error correction

CIFAR Senior Fellow **Raymond Laflamme**’s group (University of Waterloo) performs experimental demonstrations of multiple rounds of algorithmic cooling using NMR. The results of these experiments help identify the challenges for performing quantum simulations of physical systems at finite temperatures, and suggest methods that may be useful in simulating thermal open quantum systems. This result, together with their demonstrations, is a step closer towards quantum error correction.

2013
### Quantum dots controlled

CIFAR Fellow **Gregor Weihs** (Universität Innsbruck) and collaborators succeed in controlling quantum dots – semiconductor nanostructures in which motion can only take place in one dimension – more accurately than ever before. They have since used this technique to generate entangled photon pairs, which are an important resource for quantum communication.

2013
### Artificial atoms interact at a distance

CIFAR fellows demonstrate for the first time that artificial atoms can work collectively rather than independently of each other to share light. CIFAR Fellow **Alexandre Blais** (Université de Sherbrooke) and CIFAR Senior Fellow **Barry Sanders** (University of Calgary), both theoretical physicists, collaborate with CIFAR Associate **Andreas Wallraff** (ETH Zurich), an experimentalist in superconducting quantum electronics, and other researchers, to design, build and test a system of artificial atoms. They connect artificial atoms along a narrow superconducting electrical wire which serves as a waveguide. The connected atoms work as a single system, linked by the quantum interaction of exchanging photons. The interaction continues even when the artificial atoms are separated by two centimetres – a huge distance in quantum terms — and is expected to persist at even greater distances.

2013
### New model accounts for wave-like behaviour

Computer scientist and Fellow **Peter Høyer** collaborates with physicist and Senior Fellow **Barry Sanders** (both University of Calgary) and a Ph.D. student to create a new model that takes into account the wave-like behaviour of quantum particles. It uses continuous variables, which can hold any possible value within a range. The model also uses harmonic oscillators – a system taken from physics to characterize wave motion. Testing their model on a well-known quantum algorithm, the team shows that taking advantage of the natural modulation in quantum systems leads to more accurate solutions than attempting to fit quantum behaviour into a discrete model. The result implies that it is better to adapt computational problems to physical properties than the other way around.

2014
### New system performs quantum computing on encrypted data

CIFAR Fellow **Thomas Jennewein** (University of Waterloo), CIFAR Global Scholar **Anne Broadbent** (University of Ottawa) and CIFAR Global Scholar Alumnus **L. Krister Shalm** (National Institute of Standards and Technology) develop a system for carrying out quantum computing on encrypted data. The method enables quantum computers to solve complex problems using sensitive data, keeping the data encrypted throughout the process. The experiment uses single particles of light, or photons, to carry information. After sending encrypted quantum bits (qubits) to the server, the researchers demonstrate that a simple interactive process between the client and the server enables perfectly private remote quantum computations. This collaborative work is initiated at a CIFAR meeting, where discussions bridge the gap between theory and practice.

2014
### Classical physics found to be contained within quantum physics

CIFAR Fellow **Robert Raussendorf** (University of British Columbia), CIFAR Fellow **Joseph Emerson** (University of Waterloo) and collaborators achieve an important breakthrough on the power of quantum computation. They consider a particular model of quantum computation, so-called measurement-based quantum computation, and then they search for its classical counterpart. They confirm that classical physics is contained in quantum physics as a limit and that this is true for computation in particular. The result of the research emphasizes a need for better understanding of the key quantum properties that make a quantum computer work.

2014
### Quantum information shown to compress

CIFAR Senior Fellow **Aephraim Steinberg** (University of Toronto), CIFAR Global Scholar alumnus **Alex Hayat** (Technion – Israel Institute of Technology) and collaborators show that quantum information stored in a collection of identically prepared quantum bits, or qubits, can be perfectly compressed into exponentially fewer qubits without losing information. Steinberg’s team shows that the information contained in three qubits can be compressed into two, and that this compression would scale exponentially, such that only 20 qubits could store all the information about one million qubits. Selected by Physics World as one of the top ten physics breakthroughs of the year, this result suggests potential future efficiencies in quantum communications and information storage.

2015
### A new way to test quantum devices

CIFAR Fellow **Alexander Lvovsky**, Senior Fellow **Barry Sanders** (both University of Calgary) and collaborators discover a unique way of testing quantum devices to determine their function and accuracy. They develop a highly accurate method for analyzing quantum optical processes using standard optical techniques involving lasers and lenses — a discovery that may lead the way towards a quantum certification process.

2015
### A step toward quantum internet

CIFAR Senior Fellow **Wolfgang Tittel** (University of Calgary) and collaborators demonstrate that a major obstacle to building a quantum information network can be overcome. They show that particles of light, or photons, can be faithfully stored and retrieved at telecommunication wavelengths in a commercially available erbium-doped fibre. This fibre is already used in today’s communication networks; here, it is re-purposed to store quantum light. To make this discovery, the researchers cool the fibre to nearly absolute zero temperature and assess its viability for quantum storage by using “entangled” pairs of photons.

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## Raymond Laflamme awarded CAP-CRM Prize

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## Quantum Teleportation Across a Metropolitan Fibre Network

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