Spectral Addressability in a Modular Two Qubit System

Abstract

The combination of structural precision and reproducibility of synthetic chemistry is perfectly suited for the creation of chemical qubits, the core units of a quantum information science (QIS) system. By exploiting the atomistic control inherent to synthetic chemistry, we address a fundamental question of how the spin−spin distance between two qubits impacts electronic spin coherence. To achieve this goal, we designed a series of molecules featuring two spectrally distinct qubits, an early transition metal, Ti 3+ , and a late transition metal, Cu 2+ with increasing separation between the two metals. Crucially, we also synthesized the monometallic congeners to serve as controls. The spectral separation between the two metals enables us to probe each metal individually in the bimetallic species and compare it with the monometallic control samples. Across a range of 1.2−2.5 nm, we find that electron spins have a negligible effect on coherence times, a finding we attribute to the distinct resonance frequencies. Coherence times are governed, instead, by the distance to nuclear spins on the other qubit's ligand framework. This finding offers guidance for the design of spectrally addressable molecular qubits.

Magnetic, Mechanically Interlocked Porphyrin–Carbon Nanotubes for Quantum Computation and Spintronics

“…This result is expected, given the long atomic bridges connecting both metallic species, as very recently demonstrated. 15 Similar conclusions can be extracted from the EPR spectra measured on the Co derivatives, as seen in Figure 3d−f. The EPR spectra of the three derivatives can be interpreted as coming from an S = 1/2 showing a hyperfine interaction with an I = 7/2 nuclear spin.…”

“…Measurements at different temperatures shows that T m reaches a maximum of T m ≈ 25 μs for the monomer, U-por, and mac-por at around 10 K. These values are consistent with previous reports on porphyrins. 15 Therefore, the formation of the dimeric mac-por does not limit T m obtained for the monomer. Interestingly, a clear though weaker spin echo is also observed in the Cu mMINT.…”

“…This value remains roughly constant from the monomer to the mac-por and is consistent with reports for porphyrins found in the literature. 13,15 The echo obtained in the mMINT is too weak to obtain T 1 . Finally, as proof-of-concept, a field-effect transistor containing a single mMINT has been fabricated by dielectrophoresis.…”

“…The adaptability in chemical synthesis provides a wide variety of customized magnetic molecules. Some of the most studied families, specifically designed for quantum information and spintronics applications, are porphyrins, − organic radicals, − and single-ion magnets like polyoxometalates , or phthalo­cyanines. ,, One of the more daunting obstacles that remains to be removed is to place and address such molecular spins in solid-state devices in a controlled way while preserving their properties. A technically challenging approach involves the direct contact of the individual molecule to nanospaced electrodes in a transistor geometry .…”

Exchange Spin Coupling in Optically Excited States

“…Exchange spin coupling in optically excited states is relevant for understanding and controlling the optical and magnetooptical properties in a variety of nanostructured systems ranging from molecules [1][2][3][4], nanoparticles [5,6], and quantum dots [7][8][9], to solids [10]. Nanoscopic systems in which spin coupling can be controlled by laser pulses [11,12] have potential applications in spin-only information transfer, storage [11,13], and quantum information processing [14][15][16]. While many studies have contributed to the understanding of spin coupling in the ground state, both theoretically [17][18][19] and experimentally [20,21], little is known on spin coupling in optically excited states [10].…”