Daniel Esteve: Ultimate Magnetic Resonance
Abstract:
Magnetic resonance, in the form of Electronic Paramagnetic Resonance (EPR) or Nuclear Magnetic Resonance (NMR), provides powerful tools for investigating matter through the modifications of the magnetic resonance spectrum induced by spin dynamics and spin-spin interactions. Because of the weak sensitivity of Magnetic Resonance, large spin ensembles are however needed for reaching a good signal-to-noise ratio. The Quantronics group at CEA-Saclay has developed a long-standing effort to improve the sensitivity of Magnetic Resonance using quantum electrical circuits inspired from those developed for controlling and measuring superconducting qubits. A sensitive method for performing the conventional inductive detection of EPR has been first demonstrated using nanofabricated microwave resonators and quantum amplifiers adding the minimal noise authorized by the laws of physics, leading to a record spin sensitivity of 10 spins/Sqrt(Hz).
A new EPR detection method based on the direct detection of the microwave photons emitted by electronic spins in a resonator they are strongly coupled to was recently demonstrated. The signal-to-noise ratio of this method being only limited by technical imperfections, EPR on a single electronic spin could be achieved. The control and the readout of a single nuclear spin coupled to an electronic spin was also recently performed.
These experiments show that magnetic resonance is possible on individual nanosystems or individual single biological objects (at ultra-low temperature).
Bio:
Daniel Esteve, is an emeritus CEA research director in SPEC, a Condensed Matter laboratory of CEA in Saclay, south of Pqris. After a PhD in Nuclear Magnetic Resonance for probing the spin-glass like orientational phase that forms in some disordered molecular solids, he teamed with Michel Devoret and Cristian Urbina for investigating the quantum properties of a collective electrical variable, namely the phase difference across a Josephson junction coupled to a dissipative environment, following the work initiated at Berkeley in John Clarke’s lab. This was the early times of the Quantronics group.
Together with John Martinis, we demonstrated that that the superconducting phase does follow the predictions of quantum mechanics as calculated using the formalism proposed by Tony Leggett. More broadly, we were interested in Mesoscopic Physics. We explained the phenomenon of Dynamical Coulomb Blockade, operated the Single Electron pump, used Atomic sized contacts as a workhorse for testing the predictions of mesoscopic physics for conductors with a small number of conduction channels, probed Andreev states, electron-electron interactions, and last but not least developed the single Cooper pair box that later had a long legacy in terms of superconducting quantum bits. We operated in the early 2000s a superconducting quantum bit fitted with single shot readout and partly protected against decoherence, and in the early 2010s an elementary full-fledged processor. In order to find systems with a superior quantum coherence, we started to also investigate spins, which is the object of the present talk.
