Fig. 7: Nuclear-nuclear entanglement generation.
From: Bipartite entanglement in a nuclear spin register mediated by a quasi-free electron spin
a Geometric phase γg = Ω/2 acquired during a full 2π evolution of the electron spin which encloses solid angle Ω and is conditioned on \(| {\Downarrow }_{1}{\Downarrow }_{2}\rangle\). Left(right) panel shows a resonant(detuned) case with solid angle Ω = 2π(π), respectively. b Circuit diagram for generating a Bell-state between n1 and n2. Init blocks consist of three SSR windows followed by an additional post-selection, see text. L is a read-out laser-pulse. Full(hollow) circles are conditional gates on \(| \Uparrow \rangle \left(\right.| \Downarrow \rangle\), respectively. Dashed line indicate additional single-qubit gates to rotate the readout basis. c Photon histogram during read-out lasers of \(| {\Downarrow }_{1}{\Downarrow }_{2}\rangle\), \(| {\Downarrow }_{1}{\Uparrow }_{2}\rangle\), \(| {\Uparrow }_{1}{\Downarrow }_{2}\rangle\) and \(| {\Uparrow }_{1}{\Uparrow }_{2}\rangle\) resonances. The different columns show the signal after application of additional basis rotations, see (b). d Relative readout amplitudes of (c) ai/∑iai, reflecting the populations of respective nuclear spin states. Black dash-dotted line show the populations and coherences of an ideal Bell-state \((| {\Downarrow }_{1}{\Uparrow }_{2}\rangle+| {\Uparrow }_{1}{\Downarrow }_{2}\rangle )/\sqrt{2}\).
