Continuous quantum measurements: from energetic costs to critical dynamics

par Lorena Ballesteros-Ferraz (CYU)

jeudi 12 févr. 2026, 11:00 → 12:00 Europe/Paris

Katherine Johnson (1R3)

Quantum measurement lies at the heart of both the foundations and applications of quantum physics, yet the interplay between measurement strength, energetic cost, and dynamical behaviour remains an open question. In this seminar, I synthesize recent theoretical advances that explore two complementary facets of continuous quantum measurement.

The first part examines the thermodynamic costs associated with weak continuous and strong quantum measurements, uncovering a counterintuitive result: sequences of weak interactions that asymptotically reproduce ideal projective measurements require more work than a single strong measurement of equivalent informational quality. This reveals fundamental trade-offs between measurement strength, energy expenditure, and information extraction [1].

The second part focuses on the dynamical behaviour of a quantum system subjected to repeated weak measurements with post-selection. I show that complex weak values can act as dynamical control parameters, inducing discontinuities in the evolution of an auxiliary meter. These discontinuities arise at critical points where the imaginary part of the weak value vanishes, leading to changes in fixed-point stability and critical scaling behaviour reminiscent of phase transitions [2].

[1] Ferraz, L. B., & Elouard, C. (2025). Weak continuous measurements require more work than strong ones. arXiv preprint arXiv:2502.09732.
[2] Ferraz, L. B. (2025). Dynamical discontinuities in repeated weak measurements revealed by complex weak values. arXiv preprint arXiv:2511.03352.