New quantum-nano fabrication and characterization facility lab advances research and enhances community innovation and collaboration.
The University of Waterloo has officially opened its state-of-the-art Inert Atmosphere Fabrication Lab (IAFL) as part of the Quantum-Nano Fabrication and Characterization Facility (QNFCF).
Quantum-Nano Centre, 200 University Ave West, Room QNC 1201 + ZOOM Waterloo, ON CA N2L 3G1
We define a map from an arbitrary quantum circuit to a local Hamiltonian whose ground state encodes the quantum computation. All previous maps relied on the Feynman-Kitaev construction, which introduces an ancillary ‘clock register’ to track the computational steps. Our construction, on the other hand, relies on injective tensor networks with associated parent Hamiltonians, avoiding the introduction of a clock register. This comes at the cost of the ground state containing only a noisy version of the quantum computation, with independent stochastic noise. We can remedy this - making our construction robust - by using quantum fault tolerance. In addition to the stochastic noise, we show that any state with energy density exponentially small in the circuit depth encodes a noisy version of the quantum computation with adversarial noise. We also show that any ‘combinatorial state’ with energy density polynomially small in depth encodes the quantum computation with adversarial noise. This serves as evidence that any state with energy density polynomially small in depth has a similar property. As an application, we give a new proof of the QMA-completeness of the local Hamiltonian problem (with logarithmic locality) and show that contracting injective tensor networks to additive error is BQP- hard. We also discuss the implication of our construction to the quantum PCP conjecture, combining with an observation that QMA verification can be done in logarithmic depth.
Based on joint work with Anurag Anshu and Nikolas P. Breuckmann. (https://arxiv.org/abs/2309.16475)
This year, the Institute for Quantum Computing (IQC) celebrates our members Albie Chan, a PhD student at IQC who won the Dean of Science Award from the Department of Physics and Astronomy, and Nicki Shaw, senior facility microscopist at the Quantum-Nano Fabrication and Characterization Facility (QNFCF) who was awarded the Department of Chemistry’s award.
This week, 24 graduates from the Institute for Quantum Computing (IQC) will cross the stage at convocation, earning their University of Waterloo graduate degrees from engineering, math and science.
MC, 200 University Ave West, Room MC 5417
Waterloo, ON CA N2L 3G1
Supervisors: Thomas Jennewein and Norbert Lütkenhaus
Quantum-Nano Centre, 200 University Ave West, Waterloo, ON CA N2L 3G1 ZOOM ONLY
Quantum data access and quantum processing can make certain classically intractable learning tasks feasible. However, quantum capabilities will only be available to a select few in the near future. Thus, reliable schemes that allow classical clients to delegate learning to untrusted quantum servers are required to facilitate widespread access to quantum learning advantages. Building on a recently introduced framework of interactive proof systems for classical machine learning, we develop a framework for classical verification of quantum learning. We exhibit learning problems that a classical learner cannot efficiently solve on their own, but that they can efficiently and reliably solve when interacting with an untrusted quantum prover. Concretely, we consider the problems of agnostic learning parities and Fourier-sparse functions with respect to distributions with uniform input marginal. We propose a new quantum data access model that we call "mixture-of-superpositions" quantum examples, based on which we give efficient quantum learning algorithms for these tasks. Moreover, we prove that agnostic quantum parity and Fourier-sparse learning can be efficiently verified by a classical verifier with only random example or statistical query access. Finally, we showcase two general scenarios in learning and verification in which quantum mixture-of-superpositions examples do not lead to sample complexity improvements over classical data. Our results demonstrate that the potential power of quantum data for learning tasks, while not unlimited, can be utilized by classical agents through interaction with untrusted quantum entities.
Today, the UN has proclaimed 2025 as the International Year of Quantum Science and Technology (IYQ). The year-long, worldwide initiative aims to celebrate the contributions of quantum science to technological progress over the past century, raise global awareness of its importance to sustainable development in the 21st century, and ensure that all nations, including Canada, have access to quantum education and opportunities.
Quantum-Nano Centre, 200 University Ave West, Room QNC 1201 Waterloo, ON CA N2L 3G1
The entanglement structure of quantum fields is of central importance in various aspects of the connection between spacetime geometry and quantum field theory. However, it is challenging to quantify entanglement between complementary regions of a quantum field theory due to the formally infinite amount of entanglement present at short distances. We present an operationally motivated way of analyzing entanglement in a QFT by considering the entanglement which can be transferred to a set of local probes coupled to the field. In particular, using a lattice approximation to the field theory, we show how to optimize the coupling of the local probes with the field in a given region to most accurately capture the original entanglement present between that region and its complement. This coupling prescription establishes a bound on the entanglement between complementary regions that can be extracted to probes with finitely many degrees of freedom.
Based on: J. High Energ. Phys. 2023, 58 (2023), arXiv:2301.08775
The Institute for Quantum Computing (IQC) is proud to congratulate Sarah Odinotski, a PhD student in IQC and Department of Electrical and Computer Engineering at the University of Waterloo, for being selected as a Vanier Scholar this year.
The Institute for Quantum Computing (IQC) is proud to congratulate Caroline de Lima Vargas Simões, a PhD student in IQC and Department of Physics and Astronomy at the University of Waterloo, for being selected as a Vanier Scholar this year.