Quantum@SUN

Title of talk: Decoherence Limiting the Cost to Simulate an Anharmonic Oscillator

Speaker: Dr Tzula Propp

(Delft University of Technology, Netherlands)

Abstract:

Decoherence increases the efficiency with which we simulate the quantum dynamics of an anharmonic oscillator governed by the Kerr effect. As decoherence washes out the fine-grained subPlanck structure associated with phase-space quantum interference in the closed quantum system, open quantum dynamics can be more efficiently simulated using a coarse-grained finite-difference numerical integration. We tie this to the way in which decoherence recovers the semiclassical truncated Wigner approximation (TWA), which strongly differs from the exact closed-system dynamics at times when quantum interference leads to cat states and more general superpositions of coherent states. The regression in quadrature measurement statistics to semiclassical dynamics becomes more pronounced as the initial amplitude of the oscillator grows. Furthermore, this regression to classical dynamics does not have the form of a convex noise model, such as for a depolarizing noise channel, which we derive measurement statistic signatures for. Instead, closed quantum system effects interact with the open system effects, giving rise to distinct open system behavior. Both the interaction between closed and open quantum system effects leading to non-convexity and the regression to classicality increasing with macroscopicity have implications for the quantum advantage achievable on near-term NISQ devices.

Bio:

Originally hailing from San Diego, California in the US, Tzula Benjamin Propp [they/them] studied Physics and Philosophy for their bachelors degree at the College of Wooster, Ohio, and then did a PhD in Physics at the University of Oregon where their dissertation examined theoretical limits to single-photon detection. They then joined University of New Mexico’s Center for Quantum Information and Control as a National Science Foundation postdoctoral fellow to study decoherence and open quantum systems, where they completed the research they will present in this talk. As of August 2023, Tzula has joined QuTech as a postdoc in the Wehner group, researching novel quantum computation and communication applications of the quantum internet with an eye towards positive social benefit, and supporting the development of photonic clients—quantum communication devices to interface with quantum servers—with quantum optical modeling. In addition to research activities, Tzula is actively working to promote resiliency and retention of marginalized researchers in quantum through outreach programs and community organizing and mentorship, recently resulting in their co-founding of the global organization Diversity in Quantum [DiviQ.org] in 2023.

The announcement can be found here.

Title of talk: Markovian Noise Modelling and Parameter Extraction Framework for Quantum Devices

Speaker: Dean Brand

(Stellenbosch University, South Africa)

Abstract:

In recent years, Noisy Intermediate Scale Quantum (NISQ) computers have been widely used as a test bed for quantum dynamics. This work provides a new hardware-agnostic framework for modelling the Markovian noise and dynamics of quantum systems in benchmark procedures used to evaluate device performance. As an accessible example, the application and performance of this framework is demonstrated on IBM Quantum computers. This framework serves to extract multiple calibration parameters simultaneously through a simplified process which is more reliable than previously studied calibration experiments and tomographic procedures. Additionally, this method allows for real-time calibration of several hardware parameters of a quantum computer within a comprehensive procedure, providing quantitative insight into the performance of each device to be accounted for in future quantum circuits. The framework proposed here has the additional benefit of highlighting the consistency among qubit pairs when extracting parameters, which leads to a less computationally expensive calibration process than evaluating the entire device at once.

Bio:

Dean is a second-year PhD student in the Quantum Research Group of Stellenbosch University in South Africa, under the supervision of Prof. Francesco Petruccione. His current research is focussed on the intersection of quantum computing and neuromorphic computing, to find an optimal hybridisation of these technologies. Dean completed his BSc and BSc Honours at the University of the Witwatersrand, Johannesburg, majoring in astronomy, astrophysics, and theoretical physics. After this he completed a NITheCS internship with Prof. Francesco Petruccione and Prof. Ilya Sinayskiy (UKZN) which was an introductory research project on quantum computing. This led to a Master’s degree with the same supervisors at the University of KwaZulu-Natal, which was based on an application of Open Quantum Systems techniques to model the noise of IBM quantum computers. His research interests have since evolved to include machine learning and quantum algorithms, which are central to the idea and aims of neuromorphic quantum computing especially for applications such as artificial intelligence and deep learning.

The announcement can be found here.