Hexamethoxyphenalenyl as a Possible Quantum Spin Simulator: An Electronically Stabilized Neutral π Radical with Novel Quantum Coherence Owing to Extremely High Nuclear Spin Degeneracy

2013 ◽  
Vol 52 (18) ◽  
pp. 4795-4799 ◽  
Author(s):  
Akira Ueda ◽  
Shuichi Suzuki ◽  
Kenta Yoshida ◽  
Kozo Fukui ◽  
Kazunobu Sato ◽  
...  
Keyword(s):  
Nuclear Spin ◽  
Quantum Coherence ◽  
Quantum Spin ◽  
Spin Degeneracy

Hexamethoxyphenalenyl as a Possible Quantum Spin Simulator: An Electronically Stabilized Neutral π Radical with Novel Quantum Coherence Owing to Extremely High Nuclear Spin Degeneracy

2013 ◽  
Vol 125 (18) ◽  
pp. 4895-4899 ◽  
Author(s):  
Akira Ueda ◽  
Shuichi Suzuki ◽  
Kenta Yoshida ◽  
Kozo Fukui ◽  
Kazunobu Sato ◽  
...  
Keyword(s):  
Nuclear Spin ◽  
Quantum Coherence ◽  
Quantum Spin ◽  
Spin Degeneracy

scholarly journals Local and Non-Local Invasive Measurements on Two Quantum Spins Coupled via Nanomechanical Oscillations

Symmetry ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1078
Author(s):  
Dimitrios Maroulakos ◽  
Levan Chotorlishvili ◽  
Dominik Schulz ◽  
Jamal Berakdar
Keyword(s):  
Quantum Coherence ◽  
Indirect Measurement ◽  
Quantum Spin ◽  
Quantum States ◽  
Spin Interaction ◽  
First Case ◽  
Composite Quantum System ◽  
Local Quantum ◽  
Non Local ◽  
Quantum Spins

Symmetry plays the central role in the structure of quantum states of bipartite (or many-body) fermionic systems. Typically, symmetry leads to the phenomenon of quantum coherence and correlations (entanglement) inherent to quantum systems only. In the present work, we study the role of symmetry (i.e., quantum correlations) in invasive quantum measurements. We consider the influence of a direct or indirect measurement process on a composite quantum system. We derive explicit analytical expressions for the case of two quantum spins positioned on both sides of the quantum cantilever. The spins are coupled indirectly to each others via their interaction with a magnetic tip deposited on the cantilever. Two types of quantum witnesses can be considered, which quantify the invasiveness of a measurement on the systems’ quantum states: (i) A local quantum witness stands for the consequence on the quantum spin states of a measurement done on the cantilever, meaning we first perform a measurement on the cantilever, and subsequently a measurement on a spin. (ii) The non-local quantum witness signifies the response of one spin if a measurement is done on the other spin. In both cases the disturbance must involve the cantilever. However, in the first case, the spin-cantilever interaction is linear in the coupling constant Ω , where as in the second case, the spin-spin interaction is quadratic in Ω . For both cases, we find and discuss analytical results for the witness.

scholarly journals Experimental study of quantum coherence decomposition and trade-off relations in a tripartite system

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Zhe Ding ◽  
Ran Liu ◽  
Chandrashekar Radhakrishnan ◽  
Wenchao Ma ◽  
Xinhua Peng ◽  
...  
Keyword(s):  
Experimental Study ◽  
Nuclear Spin ◽  
Quantum Coherence ◽  
Quantum Systems ◽  
Spin Systems ◽  
Quantum States ◽  
Product State ◽  
Trade Off ◽  
Global Coherence ◽  
Multipartite System

AbstractQuantum coherence is the most fundamental of all quantum quantifiers, underlying other well-known quantities such as entanglement. It can be distributed in a multipartite system in various ways—for example, in a bipartite system it can exist within subsystems (local coherence) or collectively between the subsystems (global coherence), and exhibits a trade-off relation. In this paper, we experimentally verify these coherence trade-off relations in adiabatically evolved nuclear spin systems using an NMR spectrometer. We study the full set of coherence trade-off relations between the original state, the bipartite product state, the tripartite product state, and the decohered product state. We also experimentally verify the monogamy inequality and show that both the quantum systems are polygamous during the evolution. We find that the properties of the state in terms of coherence and monogamy are equivalent. This illustrates the utility of using coherence as a characterization tool for quantum states.

scholarly journals Universal dynamics of quantum spin decoherence in a nuclear spin bath

2008 ◽  
Vol 77 (17) ◽  
Author(s):  
Yi-Ya Tian ◽  
Pochung Chen ◽  
Daw-Wei Wang
Keyword(s):  
Nuclear Spin ◽  
Quantum Spin ◽  
Spin Bath ◽  
Spin Decoherence

scholarly journals Electrical control of coherent spin rotation of a single-spin qubit

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Xiaoche Wang ◽  
Yuxuan Xiao ◽  
Chuanpu Liu ◽  
Eric Lee-Wong ◽  
Nathan J. McLaughlin ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Rabi Oscillation ◽  
Quantum Spin ◽  
Spin Rotation ◽  
Nitrogen Vacancy ◽  
Single Spin ◽  
Electrical Control ◽  
Spin Qubit ◽  
Nv Centers ◽  
Coherent Spin

Abstract Nitrogen vacancy (NV) centers, optically active atomic defects in diamond, have attracted tremendous interest for quantum sensing, network, and computing applications due to their excellent quantum coherence and remarkable versatility in a real, ambient environment. One of the critical challenges to develop NV-based quantum operation platforms results from the difficulty in locally addressing the quantum spin states of individual NV spins in a scalable, energy-efficient manner. Here, we report electrical control of the coherent spin rotation rate of a single-spin qubit in NV-magnet based hybrid quantum systems. By utilizing electrically generated spin currents, we are able to achieve efficient tuning of magnetic damping and the amplitude of the dipole fields generated by a micrometer-sized resonant magnet, enabling electrical control of the Rabi oscillation frequency of NV spins. Our results highlight the potential of NV centers in designing functional hybrid solid-state systems for next-generation quantum-information technologies. The demonstrated coupling between the NV centers and the propagating spin waves harbored by a magnetic insulator further points to the possibility to establish macroscale entanglement between distant spin qubits.

scholarly journals Controllable freezing of the nuclear spin bath in a single-atom spin qubit

2020 ◽  
Vol 6 (27) ◽  
pp. eaba3442 ◽  
Author(s):  
Mateusz T. Mądzik ◽  
Thaddeus D. Ladd ◽  
Fay E. Hudson ◽  
Kohei M. Itoh ◽  
Alexander M. Jakob ◽  
...  
Keyword(s):  
Electron Spin ◽  
Nuclear Spin ◽  
Quantum Coherence ◽  
Spin Dynamics ◽  
Spin Fluctuations ◽  
Single Atom ◽  
Spin Qubits ◽  
Nuclear Dynamics ◽  
Spin Bath ◽  
Spin Qubit

The quantum coherence and gate fidelity of electron spin qubits in semiconductors are often limited by nuclear spin fluctuations. Enrichment of spin-zero isotopes in silicon markedly improves the dephasing time T2*, which, unexpectedly, can extend two orders of magnitude beyond theoretical expectations. Using a single-atom 31P qubit in enriched 28Si, we show that the abnormally long T2* is due to the freezing of the dynamics of the residual 29Si nuclei, caused by the electron-nuclear hyperfine interaction. Inserting a waiting period when the electron is controllably removed unfreezes the nuclear dynamics and restores the ergodic T2* value. Our conclusions are supported by a nearly parameter-free modeling of the 29Si nuclear spin dynamics, which reveals the degree of backaction provided by the electron spin. This study clarifies the limits of ergodic assumptions in nuclear bath dynamics and provides previously unidentified strategies for maximizing coherence and gate fidelity of spin qubits in semiconductors.

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