US 12,450,515 B2
Method for reading the spin state of a system and associated method for determining the fidelity
Pierre-André Mortemousque, Grenoble (FR); Baptiste Jadot, Grenoble (FR); Tristan Meunier, Grenoble (FR); and Matias Urdampilleta, Grenoble (FR)
Assigned to COMMISSARIAT A L'ÉNERGIE ATOMIQUE ET AUX ÉNERGIES ALTERNATIVES, Paris (FR); and CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE, Paris (FR)
Filed by COMMISSARIAT À L'ÉNERGIE ATOMIQUE ET AUX ÉNERGIES ALTERNATIVES, Paris (FR); and CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE, Paris (FR)
Filed on Dec. 23, 2021, as Appl. No. 17/560,451.
Claims priority of application No. 2014084 (FR), filed on Dec. 23, 2020.
Prior Publication US 2022/0198314 A1, Jun. 23, 2022
Int. Cl. G06N 10/60 (2022.01); G01N 24/00 (2006.01)
CPC G06N 10/60 (2022.01) [G01N 24/00 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A method for measuring a spin state of two charged particles being able to adopt a first spin state noted S, a second spin state noted T+, a third spin state noted T0 and a fourth spin state noted T−, the two charged particles being contained in a system, comprising a first quantum dot and a second quantum dot characterised by a first parameter Γ relative to a potential barrier separating the first and second quantum dots and a second parameter ε corresponding to a difference in energy between a fundamental state of the first quantum dot and a fundamental state of the second quantum dot, a couple formed by values of the first and second parameters defining an operating point of the system as a function of which the system adopts a first charge state noted (1,1) wherein each quantum dot contains a charged particle, a second charge state noted (2,0) wherein the first quantum dot contains two charged particles or a third charge state noted (0,2) wherein the second quantum dot contains two charged particles, the operating point of the system being initially in a first operating point corresponding to the first charge state (1,1) of the system and for which the first S, the second T+, the third T0 and the fourth T− spin states are eigenstates of the spin of the two charged particles, the method comprising:
a first step of modification of the operating point of the system during which the operating point is displaced from the first operating point to a second operating point corresponding to the second charge state (2,0) or to the third charge state (0,2), the energy level of the first spin state S and the second spin state T+ forming an avoided crossing during the displacement from the first operating point to the second operating point, the modification of the operating point taking place non-adiabatically during a passage of the avoided crossing such that, during said first step, the system transits from the first charge state (1,1) to the charge state corresponding to the second operating point when the two charged particles contained in the system are in the first spin state S and the system is maintained in the first charge state (1,1) for the other spin states;
a first step of measuring the charge state of the system, the spin state of the two charged particles at the first operating point being the first spin state S if the charge state of the system measured is equal to the charge state corresponding to the second operating point, the operating point being once again displaced to the first operating point;
a second step of modification of the operating point of the system during which the operating point is displaced from the first operating point to the second operating point, the modification of the operating point taking place adiabatically during the passage of the avoided crossing such that, during said second step, the system transits from the first charge state (1,1) to the charge state corresponding to the second operating point when the two charged particles contained in the system are in the second spin state T+ and is maintained in the first charge state (1,1) for the other spin states;
a second step of measuring the charge state of the system, the spin state of the two charged particles at the first operating point being the second spin state T+ if the charge state of the system measured is equal to the charge state corresponding to the second operating point, the operating point being once again displaced to the first operating point;
a third step of modification of the operating point of the system during which the operating point is displaced from the first operating point to the second operating point, the modification of the operating point taking place non-adiabatically during the passage of the avoided crossing;
a waiting step at a waiting operating point corresponding to a charge state identical to that of the second operating point during a predefined time, step during which the system transits from the first charge state (1,1) to the charge state corresponding to the second operating point when the two charged particles are in the third spin state T0 and is maintained in the first charge state for the fourth spin state T−;
a third step of measuring the charge state of the system, the spin state of the two particles at the first operating point being the third spin state T0 if the charge state of the system measured is equal to the charge state corresponding to the second operating point and the fourth spin state T− if the charge state of the system measured is equal to the first charge state.