Coherent manipulation and quantum phase interference in a fullerene-based electron triplet molecular qutrit

Abstract

High-spin magnetic molecules are promising candidates for quantum information processing because their intrinsic multiplicity facilitates information storage and computational operations. However, due to the absence of suitable sublevel splittings, their susceptibility to environmental disturbances and limitation from the selection rule, the arbitrary control of the quantum state of a molecular electron multiplet has not been realized. Here, we exploit the photoexcited triplet of C70 as a molecular electron spin qutrit with pulsed electron paramagnetic resonance. We prepared the system into 3-level superposition states characteristic of a qutrit and validated them by the tomography of their density matrices. To further elucidate the coherence of the operation and the nature of the system as a qutrit, we demonstrated the quantum phase interference in the superposition. The interference pattern is further interpreted as a map of possible evolution paths in the space of phase factors, representing the quantum nature of the 3-level system.

Using Molecular Design to Enhance the Coherence Time of Quintet Multiexcitons Generated by Singlet Fission in Single Crystals

“…Several other qualities of the 5 (TT) state also make it attractive for QIS applications. Due to its high spin multiplicity, 5 (TT) can be utilized as a five-level qudit, which may facilitate greater storage and processing of quantum information compared to systems with fewer accessible quantum levels. − The 5 (TT) state can also be photogenerated on-demand at arbitrary locations, potentially with high spatial resolution using nanophotonic architectures. , This offers advantages over spin qubits based on defect centers, such as nitrogen-vacancy centers in diamond, , for which the placement of defects at specific sites in the lattice remains challenging. Moreover, the high binding energy of excitons in organic semiconductors may enable long 5 (TT) lifetimes and, in turn, allow quantum coherent control at room temperature provided that sources of spin decoherence can be suppressed.…”

Implementation of Quantum Level Addressability and Geometric Phase Manipulation in Aligned Endohedral Fullerene Qudits

“…Evidenced by the electron spin properties of N@C 60,70 , [2] Sc@C 82 , Y@C 82 , La@C 82 , [3, 4] etc., the structure essentially extends the coherence time, as it diminishes the relaxation processes related to fluctuations of environment. Moreover, the carbonaceous elemental composition can effectively sustain the spin coherence due to the zero nuclear spin of the 12 C. As a result, some electron‐spin‐based quantum applications, including molecular quantum computing, [5, 6] molecular atomic clocks, [7] and quantum metrology and sensing, [8, 9] have been proposed.…”

Triplet-radical spin entanglement: potential of molecular materials for high-temperature quantum information processing

“…Hence, quantum gate operations at higher temperatures are still an inevitable obstacle to overcome for a practical QIP device 4 . Optical excitations, especially in organic materials, could be one of the solutions, offering larger energy scales for coherent interactions against incoherent thermal noise due to the high temperature (~77 K, the boiling point of liquid nitrogen) [5][6][7] . By using optical excitations, we can also avoid the decoherence induced by the external electrodes conventionally used for the control of electrons 8 .…”

“…For radical-bearing molecules, the long-lived triplet (spin-1) can be formed by optical excitations and intersystem crossing (ISC, from the singlet excited state to the triplet ground state) 14 , which can interact via exchange interactions coherently with the radical spin. The triplet plays a role not only as a qutrit (a 3-level quantum system), which can lead to increased security, greater channel capacities, and more efficient gate operations 7 , but also a coupler for controlling the interaction between radicals 15 . Spin states such as a quartet (one radical coupled with a triplet), as shown in Fig.…”