ELFT HÍRADÓ

[Makk Péter <peter.makk AT gmail.com>]

 Szeretettel meghívunk minden érdeklődőt a BME Fizika tanszék nanofizika
szemináriumára:

Vishal Ranjan
(CEA Saclay, Quantronics Group, FR)
"High sensitivity quantum-limited electron spin resonance".

Helyszín: BME Fizika tanszék
F1 épület, 1. emelet szemináriumi szoba
Időpont: 2019.november 7, 10:00

Abstract:
In a conventional electron spin resonance (ESR) spectrometer based on the
inductive detection method, the paramagnetic spins precess in an external
magnetic field B0 radiating weak microwave signals into a resonant cavity
which are subsequently amplified and measured. Despite its widespread
use, ESR spectroscopy has limited sensitivity, and large amounts of spins
are necessary to accumulate sufficient signal. Most conventional ESR
spectrometers operate at room temperature and employ three-dimensional
cavities. At X-band, they require approximately 10^13 spins to obtain
sufficient signal in a single echo [1]. Enhancing this sensitivity to
smaller spin ensembles and eventually the single spin limit is highly
desirable.
Exploiting recent progress in circuit-quantum electrodynamics, we have
combined high quality factor superconducting micro-resonators and
noise-less Josephson Parametric Amplifiers to perform ESR spectroscopy at
millikelvin temperatures, reaching a new regime where the sensitivity is
limited by the quantum fluctuations of the microwave field. Quantum
fluctuations of the field also affect directly the spin dynamics via
Purcell effect : spin relaxation occurs dominantly by spontaneous emissions
of microwave photons. Based on these principles [2-4], we first show an
unprecedented measurement sensitivity of 10 spins/sqrt(Hz) for unit SNR in
an inductive-detection ESR with an ensemble of Bismuth donors in Silicon
[5]. This high sensitivity enables us to characterize the coherence
properties of an ensemble of donors in close proximity ( 50- 100 nm) to the
silicon surface, with spatial resolution. We identify surface magnetic and
electric noise as the main decoherence sources in our device. At the
so-called "clock transition", the coherence time approaches 1s, which is
the longest reported for an electron spin close to a surface [6].

[1] A. Schweiger and G. Jeschke, Principles of pulse electron paramagnetic
resonance (Oxford University Press, 2001).
[2] P. Haikka, Y. Kubo, A. Bienfait, P. Bertet, K. Moelmer, Phys. Rev. A
95, 022306 (2017).
[3] A. Bienfait, J. Pla, Y. Kubo, M. Stern, X. Zhou, C.C. Lo,C.Weis, T.
Schenkel, M. Thewalt, D. Vion, D. Esteve, B. Julsgaard, K.
Moelmer, J. Morton, and P. Bertet, Nature Nanotechnology 11, 253 (2015).
[4] S. Probst, A. Bienfait, P. Campagne-Ibarcq, J. J. Pla, B. Albanese, J.
F. Da SilvaBarbosa, T. Schenkel, D. Vion, D. Esteve, K.
Mlmer, J. J. L. Morton, R. Heeres, P.Bertet, Appl. Phys. Lett. 111, 202604
(2017)
[5] V. Ranjan et. al., in preparation (2019)
[6] V. Ranjan et. al., in preparation (2019)

üdvözlettel
Makk Péter