En francais

Four University of Waterloo researchers, including Dr. Michael Reimer, a faculty member at the Institute for Quantum Computing and a professor in the Department of Electrical and Computer Engineering, were awarded funding earlier this month from the Ontario government for innovative research that ranges from cleaning up arsenic-laden mine waste, treating potential virus outbreaks, and using artificial intelligence to protect valuable financial data.

Tuesday, April 2, 2024 2:30 pm - 3:30 pm EDT (GMT -04:00)

Quantum Computational Advantages in Energy Minimization

IQC Special Colloquium Leo Zhou, California Institute of Technology

Quantum-Nano Centre, 200 University Ave West, Room QNC 1201 Waterloo, ON CA N2L 3G1

Finding the minimum of the energy of a many-body system is a fundamental problem in many fields. Although we hope a quantum computer can help us solve this problem faster than classical computers, we have a very limited understanding of where a quantum advantage may be found. In this talk, I will present some recent theoretical advances that shed light on quantum advantages in this domain. First, I describe rigorous analyses of the Quantum Approximate Optimization Algorithm applied to minimizing energies of classical spin glasses. For certain families of spin glasses, we find the QAOA has a quantum advantage over the best known classical algorithms. Second, we study the problem of finding a local minimum of the energy of quantum systems. While local minima are much easier to find than ground states, we show that finding a local minimum under thermal perturbations is computationally hard for classical computers, but easy for quantum computers. These results highlight exciting new directions in leveraging physics-inspired algorithms to achieve quantum advantages in broadly useful problems.

Thursday, April 11, 2024 1:30 pm - 2:30 pm EDT (GMT -04:00)

Breaking ergodicity: quantum scars, quantum many-body scars and regular eigenstates

IQC Special Colloquium - Ceren B. Dag Harvard University

Quantum-Nano Centre, 200 University Ave West, Room QNC 0101 Waterloo, ON CA N2L 3G1

Quantum many-body scars (QMBS) consist of a few low-entropy eigenstates in an otherwise chaotic many-body spectrum and can weakly break ergodicity resulting in robust oscillatory dynamics. The notion of QMBS follows the original single-particle scars introduced within the context of quantum billiards, where scarring manifests in the form of a quantum eigenstate concentrating around an underlying classical unstable periodic orbit. A direct connection between these notions remains an outstanding question. Here, I will first show that a spinor condensate, owing to its collective interactions, is amenable to the diagnostics of scars. We characterize this system's rich dynamics, spectrum, and phase space, consisting of both regular and chaotic states. The former are low in entropy, violate the Eigenstate Thermalization Hypothesis, and can be traced back to integrable effective Hamiltonians, whereas most of the latter are scarred by the underlying classical unstable periodic orbits, while satisfying Eigenstate Thermalization Hypothesis. I will exhibit evidence on how the existing QMBS in the literature are akin to the regular states, rather than the quantum scars. Then I will move on to introduce a spatially many-body model with a mean-field limit by decreasing the range of the interactions. Remarkably, we find that unstable periodic orbits affect the early-time many-body dynamics giving rise to a new type of QMBS. I will classify the QMBS in two main classes, discuss their distinct properties, and show how both QMBS states show up in our model in different parameter regimes. This talk aims (i) to clarify the connection of QMBS to quantum scars and regular eigenstates, and (ii) illustrate the fundamental principle of classical-quantum correspondence in a many-body system, and its current limitations.

En francais

University of Waterloo researchers combine Nobel prize winning concepts to achieve scientific breakthrough.

Researchers at the University of Waterloo’s Institute for Quantum Computing (IQC) have brought together two Nobel prize winning research concepts to advance the field of quantum communication.

En francais

The National Killam Program administered by the National Research Council of Canada (NRC) announces Dr. Adam Wei Tsen as the recipient of the 2024 Dorothy Killam Fellowship. This prestigious honour provides $80,000 for up to two years in support for dedicated research time to scholars “whose superior, ground-breaking, best-in-class research stands to have significant impact on a national or global scale.” 

Tsen is a professor at the Institute for Quantum Computing (IQC) and the Department of Chemistry at the University of Waterloo. His research focuses on the study of various two-dimensional (2D) quantum materials and making new magnetically active molecules for quantum material applications, including quantum computing and quantum information.

The (Quantum) Signal and the Noise: towards the intermediate term of quantum computation

University of Waterloo, 200 University Ave West QNC 0101 + ZOOM

Can we compute on small quantum processors? In this talk, I explore the extent to which noise presents a barrier to this goal by quickly drowning out the information in a quantum computation. Noise is a tough adversary: we show that a large class of error mitigation algorithms -- proposals to "undo" the effects of quantum noise through mostly classical post-processing – can never scale up. Switching gears, we next explore the effects of non-unital noise, a physically natural (yet analytically difficult) class of noise that includes amplitude-damping and photon loss. We show that it creates effectively shallow circuits, in the process displaying the strongest known bound on average convergence of quantum states under such noise. Concluding with the computational complexity of learning the outputs of small quantum processors, I will set out a program for wrapping these lower bounds into new directions to look for near-term quantum computational advantage. 

En francais

The Government of Canada has invested nearly $7M into quantum projects at the University of Waterloo through recently announced NSERC Alliance Grants. The grants, awarded by the Natural Sciences and Engineering Research Council of Canada (NSERC), encourage university researchers to collaborate with partner organizations from across the private, public or not-for-profit sectors.

Thursday, March 14, 2024

Quantum Community

En francais

With a focus on collaboration and community, the Institute for Quantum Computing (IQC) is proud to host regular social events for our members. While media and popular culture often portray the image of a lone researcher working late nights in a lab or at a computer to make breakthroughs, the more realistic portrayal of new ideas and discoveries can be encompassed through partnerships and teamwork.