Monday, February 5, 2024 2:30 pm - 3:30 pm EST (GMT -05:00)

Achieving quantum sensing limits in noisy environment

IQC Colloquium - Sisi Zhou, The Perimeter Institute

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

 Quantum metrology studies estimation of unknown parameters in quantum systems. The Heisenberg limit of estimation precision 1/N, with N being the number of probes, is the ultimate sensing limit allowed by quantum mechanics that quadratically outperforms the classically-achievable standard quantum limit 1/√N. The Heisenberg limit is attainable using multi-probe entanglement in the ideal, noiseless case. However, in presence of noise, many quantum systems only allow a constant factor of improvement over the standard quantum limit. To elucidate the noise effect in quantum metrology, we prove a necessary and sufficient condition for achieving the Heisenberg limit using quantum controls. We show that when the condition is satisfied, there exist quantum error correction protocols to achieve the Heisenberg limit; when the condition is violated, no quantum controls can break the standard quantum limit (although quantum error correction can be used to maximize the constant-factor improvement). We will also discuss the modified sensing limits when only restricted types of quantum controls can be applied. 

Monday, November 20, 2023 2:30 pm - 3:30 pm EST (GMT -05:00)

Nature-Inspired Nanotechnologies

IQC Seminar - Jong-Souk Yeo, Yonsei University

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

Biomimetic or nature-Inspired technologies are referring to the emerging fields where innovations are strongly inspired by the wisdom from nature or biological systems. Multiple levels of approaches are feasible from nature-inspiration – adaptation of how nature works, adoption of what nature provides, or replication of natural processes and functionalities for eco-friendly, sustainable, and highly efficient technologies. In this talk, nature-inspired approaches will be introduced for the nano-bio and nano-IT convergence research in the areas of nanostructure-cell interactions [1], nano-bio sensorics [2], biomimetic optical nanostructures [3], stretchable electronics [4], quantum plasmonics [5], and neuromorphic semiconductor technologies. Along with the research, recent efforts at Yonsei University will be introduced about the School of Integrated Technology where research and education are organically integrated for the technology convergence, and Yonsei Science Park where innovation ecosystem is established for IT-Bio Cluster Hub hosting Global Bio Campus and IBM quantum computer. This research was supported by the MSIT (Ministry of Science and ICT), Korea, under the ICT Consilience Creative program (IITP-2019-2017-0-01015) supervised by the IITP (Institute for Information & communications Technology Planning & Evaluation), the Ministry of trade, Industry and Energy (MOTIE) and Korea Institute for Advancement of Technology (KIAT) through the International Cooperative R&D program (Project No. P0019630) and by the Human Frontier Science Program (RGP0047/2019).

Monday, October 16, 2023 3:00 pm - 4:00 pm EDT (GMT -04:00)

Fully-quantum learning: Comparison of unknown unitary channels with multiple uses

IQC Colloquium - Mio Murao, The University of Tokyo

Quantum Nano Centre (QNC) Room 0101 200 University Ave West, Waterloo Ontario

Please note start time 3:00 PM

Efficiently learning properties of unknown quantum objects is a fundamental task in quantum mechanics and quantum information. When there are two unknown quantum objects, and if we want to learn just the relationship between the objects, a method to directly compare the two objects without identifying their descriptions is preferable, especially when the number of available copies of each target object is limited. In this work, we investigate the comparison of unknown unitary channels with multiple uses of the unitary channels based on the quantum tester formalism.  We obtain the optimal minimum-error strategy and the optimal unambiguous strategy of unitary comparison of two unknown d-dimensional unitary channels when the number of uses of the channels satisfies a certain condition. These optimal strategies are implemented by parallel uses of the unitary channels, even though all sequential and adaptive strategies implementable by the quantum circuit model are considered. When the number of the smaller uses of the unitary channels is fixed, the optimal averaged success probability is achieved by a certain number of uses of the other channel. This feature contrasts with the case of pure-state comparison, where adding more copies of the unknown pure states always improves the optimal averaged success probability. It highlights the difference between corresponding tasks for states and channels, which has been previously shown for quantum discrimination tasks.  

Reference: Y. Hashimoto, A. Soeda and M. Murao, Comparison of unknown unitary channels with multiple uses, arXiv:2208.12519

Monday, September 25, 2023 2:30 pm - 3:30 pm EDT (GMT -04:00)

Quantum Fine-Grained Complexity

Quantum Nano Centre (QNC) Room 0101, 200 University Avenue West, Waterloo, ON

IQC Colloquium, Harry Buhrman - QuSoft

One of the major challenges in computer science is to establish lower bounds on the resources, usually time, that are needed to solve computational problems. This holds in particular for computational problems that appear in practise. One way towards dealing with this situation is the study of fine- grained complexity where we use special reductions to prove time lower bounds for many diverse problems based on the conjectured hardness of some key problems.

Monday, July 17, 2023 2:30 pm - 3:30 pm EDT (GMT -04:00)

Simulation, control and sensing in open quantum systems

IQC Colloquium - Nir Bar-Gill, Applied Physics and Physics, The Hebrew University

In this talk I will address these topics through the platform of nitrogen-vacancy (NV) spins in diamond, in the context of purification (or cooling) of a spin bath as a quantum resource and for enhanced metrology and sensing.

IQC Colloquium on ZOOM - Mark Zhandry, NTT Research

Public verification of quantum money has been one of the central objects in quantum cryptography ever since Wiesner's pioneering idea of using quantum mechanics to construct banknotes against counterfeiting. In this talk, I will discuss some recent work giving both attacks and new approaches to building publicly verifiable quantum money.

Monday, May 15, 2023 2:30 pm - 3:30 pm EDT (GMT -04:00)

Quantum thermal machines at strong coupling

IQC Colloquium - Dvira Segal, University of Toronto

Rethinking the operation principles of thermal machines in the nanoscale and quantum domain, we focus on a continuous machine operating in steady state, the quantum absorption refrigerator (QAR), and examine three key questions: (i) How does the strong system-bath interaction affect the device's operation? (ii) What can we learn about the machine from current noise? (iii) What is the impact of coherences within the working fluid on the performance of the quantum machine? 

Monday, March 27, 2023 4:00 pm - 5:00 pm EDT (GMT -04:00)

Reactive Conjugated Polymers for Selective Dispersion of Carbon Nanotubes

IQC Colloquium, Alex Adronov McMaster University

Single-Walled Carbon Nanotubes (SWNTs) exhibit a number of unique mechanical, thermal, and electronic properties that render them useful for numerous applications, ranging from molecular electronics to nano-scale construction materials.  However, SWNTs are highly insoluble and are devoid of reactive functionality, posing major limitations to their modification, manipulation, and ...

Monday, February 27, 2023 2:30 pm - 3:30 pm EST (GMT -05:00)

Spin Qubits in Semiconductors: Current Status and Future Directions

IQC Colloquium featuring Xuedong Hu Department of Physics, University at Buffalo, SUNY

Research on the physical implementation of quantum computing has made dramatic progress over the past decade, spearheaded by superconducting qubits and trapped ion qubits, to the degree that small-scale quantum information processors are now within reach. Studies of semiconductor spin qubits, which have often been considered one of the most promising in the long term from the perspective of scalability, have also yielded some important results in the past decade, demonstrating exceptional coherence properties for single spins confined in quantum dots and donors and high-fidelity single-qubit gates. ...

Monday, January 23, 2023 10:30 am - 12:00 pm EST (GMT -05:00)

Silicon Colour Centres

IQC Colloquium Featuring Dr. Stephanie Simmons - Photonic

The future global quantum internet will require high-performance matter-photon interfaces. The highly demanding technological requirements indicate that the matter-photon interfaces currently under study all have potentially unworkable drawbacks, and there is a global race underway to identify the best possible new alternative. For overwhelming commercial and quantum reasons, silicon is the best possible host for such an interface. Silicon is not only the most developed integrated photonics and electronics platform by far, isotopically purified silicon-28 has also set records for quantum lifetimes at both cryogenic and room temperatures ...