BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69e22ce0beee2 DTSTART:20260317T140000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:Elements Room SUMMARY:ICFO | MARTA CAGETTI CLASS:PUBLIC DESCRIPTION:In this thesis we present an ultrasensitive\, fast and widely t unable charge detection architecture\, suitable for the readout of both el ectronic states and mechanical motion. The platform is implemented in susp ended carbon nanotube (CNT) devices. Our approach employs a radiofrequency (RF) readout scheme operating without impedance matching\, thereby avoidi ng one of the main practical limitations of conventional reflectometry. Th e readout achieves charge sensitivities exceeding state of the art RF dete ction techniques\, while relying on a comparatively simple measurement set up. The device is based on an integrated single nanotube platform\, in whi ch a system of gate defined quantum dots and a proximal quantum dot based charge sensor are hosted in the same suspended CNT and separated by a shor t metallic drain electrode. The drain is connected to an RLC resonator wit h a resonance frequency fRLC approximately 1.25 MHz and a bandwidth of 50 kHz\, enabling RF readout of the charge sensor current at the circuit reso nance. This geometry provides strong capacitive coupling while maintaining independent electrostatic control of the sensor operating point and of th e target quantum dots. Using this platform\, we achieve self charge sensit ivities of order 10^-7 e/sqrt(Hz) and an exceptionally low single shot inf idelity\, 1 - F approximately 10^-15\, for an integration time tau approxi mately 3.5 microseconds. Beyond the readout of electronic charge transitio ns in the target quantum dots\, the same charge sensor provides highly sen sitive access to the mechanical degrees of freedom of the suspended nanotu be in the system region. Mechanical displacement is transduced into variat ions of the charge sensor quantum dot conductance\, enabling measurements ranging from driven nonlinear dynamics to thermomechanical motion in the f ew phonon regime. Crucially\, our platform allows operation in a regime wh ere electromechanical backaction\, which is typical of suspended carbon na notubes hosting quantum dots\, is strongly suppressed. This addresses one of the central challenges of CNT based nanomechanics: in single dot electr omechanical architectures\, achieving strong or ultrastrong coupling gener ally requires operation near charge degeneracy\, where coupling to electro nic reservoirs and stochastic tunneling lead to excessive dissipation\, fr equency noise and a pronounced reduction of the mechanical quality factor. Indeed\, in previous experiments in the ultrastrong coupling regime\, mea surement backaction broadened the mechanical response to the point of obsc uring access to the intrinsic mechanical properties. In contrast\, in our devices we maintain high readout sensitivity without any observable degrad ation of the mechanical quality factor Q\, enabling quantitative spectrosc opy of the resonator while preserving its intrinsic mechanical properties. This capability to perform quantitative spectroscopy of a nanomechanical resonator coupled to a two level system in the few phonon regime constitut es a key requirement for advancing towards experiments in the quantum regi me\, where preserving intrinsic mechanical coherence is essential. The hig h degree of tunability of our platform enables precise control of charge o ccupation\, tunnel couplings and electrostatic potentials\, allowing syste matic studies of electromechanical coupling from the single electron regim e in a simple quantum dot to the double quantum dot configuration. We demo nstrate ultrastrong electromechanical coupling\, opening the door to futur e work on nonlinear nanomechanics\, mechanical qubits\, quantum delocaliza tion and carbon nanotube based quantum simulation.\n \;\nTuesday March 17\, 15:00 h. ICFO Elements Room \nThesis Director: Prof. Dr. Adrian Bach told and Dr. Stefan Forstner DTSTAMP:20260417T125144Z END:VEVENT END:VCALENDAR