Josh Folk [University of British Columbia]

Abstract: Quantum measurement in solid-state devices is often associated with strongly biased detectors, whose nonequilibrium noise dephases the measured system. Here I discuss a different form of backaction: a near-equilibrium charge detector that modifies quantum-dot tunneling through many-body correlations. In a pair of capacitively coupled GaAs quantum dots, tunneling onto a weakly coupled system dot abruptly changes the scattering potential of a strongly coupled detector dot, driving an Anderson orthogonality catastrophe in the detector Fermi sea. A large bias across the system dot exposes the energy dependence of the tunneling rates, while tuning the detector through resonance varies the measurement strength. Far from resonance, the occupation remains near N=1/2 across the bias window, as expected for non-interacting tunneling to symmetrically coupled leads. Near resonance, strong backaction suppresses resonant tunneling and enhances inelastic processes, replacing this plateau with a gradual transition from N=0 to N=1 across the bias window. Time-resolved charge sensing, continuous detector readout, and direct transport measurements capture the predicted AOC phenomenology and enable extraction of the AOC exponent, while systematic deviations from the theory point to additional many-body physics beyond the simplest model. These results show that measurement backaction can arise from equilibrium many-body correlations, not only from classical detector noise.

Research interests: 2D materials, quantum devices, quantum thermodynamics

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Notes:

• Main talk will begin @ 11:30 am in PAB 102/103
• Boxed lunch will available @ 12:30 pm in PAB 102/103
• Video Recordings once Speaker approved, will be available on our youtube channel