Quantum metrology with interacting many-body systems: Fundamental bounds and attainability
||Conferences - Seminars
Please join us for the QSE Center Quantum Seminar with Prof. Martí Perarnau-Llobet from University of Geneva who will speak on Thurdsay, November 30, about "Quantum metrology with interacting many-body systems".
Location: BS 270
Pizzas will be available before the seminar at 12:00. All PhDs, postdocs, students, and PIs are welcome to join us.
TITLE: Quantum metrology with interacting many-body systems: Fundamental bounds and attainability
Standard quantum metrology protocols exploit delicate quantum states, like entangled or squeezed states, to enhance the precision of measurements beyond the standard shot-noise limit. Usually, this advantage is lost in the presence of dissipation or noise. A potential avenue to overcome this limitation is to consider many-body interacting systems, where the presence of interactions can lead to non-trivial open dynamics and steady states that can be useful for metrology. A prominent example is critical quantum metrology, which uses a probe close to a (quantum) phase transition for very precise measurements.
In this talk, I will present progress in this direction by considering the estimation of parameters, e.g. temperature or magnetic fields, from measurements of a quantum probe in thermal equilibrium. For the probe, we will consider an interacting few or many-body quantum system. I will show a general bound on the measurement precision (the Quantum Fisher Information) valid for arbitrary Hamiltonians of the probe, which shows a quadratic scaling with the number of bodies. Despite a formal resemblance with the Heisenberg limit, we will see that this bound can be saturated by purely classical (i.e. commuting) interacting Hamiltonians. A quantum advantage becomes possible for gapped Hamiltonians in the low temperature regime. I will then discuss how to engineer optimal probes, featuring locally interacting two-body Hamiltonians, that can approach such limits for the estimation of relevant magnitudes (e.g. magnetic fields and temperature). Finally, I will discuss the crucial role of feedback and measurement adaptativity to saturate these bounds in the presence of prior uncertainty.
This talk is based on joint work with Paolo Abiuso (soon to appear in arxiv), and also on arXiv:2211.01934
Martí Perarnau-Llobet is an Assistant Professor at the University of Geneva, since May 2020. Previously, he was postdoc at the Max Planck Institute for Quantum Optics in Garching (2016-2020) in the Theory group of Ignacio Cirac, and did the Phd in ICFO (2012-2016) in Acín's group.