ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarGali ÁdámWigner RCP SZFIObservation of a quantum bit in 
HungaryTuesday, 17 January 2023, 10:00, KFKI Campus, Bldg. 1, 2nd floor, 
Conference RoomA qubit is a two-state (or two-level) quantum-mechanical 
system which is the basic unit of quantum information. The most simple 
realisation of this two-state system is the electron spin which may exist in 
a superposition state. We observe the coherent oscillation of a single 
electron spin at room temperature. The single electron spin is realised by 
the negatively charged nitrogen-vacancy (NV) centre in diamond. Room 
temperature qubits are rare species; the well-isolated diamond NV centre's 
electron spin has millisecond longitudinal T1 lifetime at room temperature. 
We will explain this feature by the large energy gap between the triplet 
ground state and singlet shelving state and the coupling of phonons to the 
electron spin with relatively high energy phonons that exhibits a double 
Orbach-process, in stark contrast to textbook cases. The coherence time of 
the electron spin (T2*) is shortened with respect to T1 time due to the 
presence of nuclear spins of nitrogen-15 and carbon-13 isotopes. In 
particular, we observe about 15 microseconds T2* time in our system. The 
initialisation and read-out of the electron spin is realised by optical means 
with harnessing the spin-selective fluorescence and optical 
spin-polarisation. We explain this feature of the centre by a delicate 
electron-phonon coupling of the shelving singlet state which results in a 
highly spin-selective intersystem crossing towards the ms=0 state of the 
triplet ground state. Finally, we show that 700,000 photons/second are 
emitted from a single NV centre from a diamond nanopillar structure. This 
emission is mostly dominated by the phonon sideband but the photon count of 
the coherent zero-phonon-line emission yields about 25,000 photons/second 
which is a good starting point to realise a spin-photon interface from this 
system at cryogenic temperatures.Join Zoom 
Meetinghttps://wigner-hu.zoom.us/j/87171121402?pwd=S2c3TGQvcERNT2RSMnRRNTN0NUh4UT09Meeting
 ID: 871 7112 1402Passcode: 630300 Minden érdeklődőt szívesen látunk! - 
Everyone is welcome to attend.Attila Nagysem-admin AT szfki.hu