Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session S36: Quantum Molecular NanomagnetsInvited
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Enrique Del Barco, Univ of Central Florida Room: BCEC 205C |
Thursday, March 7, 2019 11:15AM - 11:51AM |
S36.00001: Forbidden Transitions in Molecular Nanomagnets Invited Speaker: Jonathan Friedman Selection rules typically arise from the constraints imposed by conservation laws. In electron-spin resonance spectroscopy, the standard single-photon-transition selection rule Δm = 0,±1 arises from angular momentum conservation. Such selection rules can be lifted when the magnetic quantum number of the spin system under study is not a good quantum number. In molecular nanomagnets (MNMs), magnetic anisotropy can lead to a preferred (easy) axis of orientation for the molecule’s spin, giving rise to an anisotropy barrier between “up” and “down” states. In addition, transverse anisotropy breaks the system’s symmetry, leading to state mixing and tunneling between spin states. Thus, tunneling can lead to the observation of forbidden transitions that strongly violate selection rules. I will report studies by my group of two MNMs that exhibit such highly forbidden transitions. In the Ni4 MNM, a spin-4 system, we observe single-photon transitions in which the magnetic moment changes by as much as ~7 hbar, nearly reversing the molecule’s spin [1]. In addition, we observe direct transitions between tunnel-split states in this MNM, allowing us to precisely determine its transverse anisotropy [2]. In the Cr7Mn MNM, a spin-1 system, there is a large tunnel splitting lifting the zero-field ground-state degeneracy. The two lowest states then have the structure of an atomic-clock transition in which the transition frequency is to first order independent of magnetic field, making the system largely immune to the decohering effects of external-field fluctuations. We find that the decoherence time T2 is enhanced by a factor of three in the vicinity of this clock transition in Cr7Mn. |
Thursday, March 7, 2019 11:51AM - 12:27PM |
S36.00002: Coherent manipulation of three spin qubits in a GdW30 single-ion magnet Invited Speaker: Fernando Luis Implementing quantum computation with spins faces the challenge of increasing the number of qubits while keeping errors under control. Even the simplest algorithm implies coupling two or more qubits in a controlled manner. However, dipolar interactions are also an important source of decoherence [1]. Here, we explore a way to scale up quantum resources, without introducing additional decoherence, by integrating several electron spin qubits in a single magnetic ion with spin S > ½. This approach is illustrated with a [Gd(H2O)P5W30O110]12- polyoxometalate single-ion magnet [2]. Electron paramagnetic resonance experiments have been performed on molecules diluted in a crystal of the diamagnetic isostructural derivative [Y(H2O)P5W30O110]12-. The seven allowed transitions between the 2S+1=8 spin states have been separately addressed and its spin coherence T2 and spin-lattice relaxation T1 rates measured. Rabi oscillations have been observed for all transitions. The spin states of each Gd3+ ion can then be mapped onto the states of three addressable qubits (or, alternatively, of a d = 8-level molecular “qudit”), for which the seven allowed transitions form a universal set of operations. Within this scheme, one of the coherent oscillations observed experimentally provides an implementation of a controlled-controlled-NOT (or Toffoli) three-qubit gate. We also propose a way to implement a simple quantum error correction code using this single-ion "processor". Our findings [3] open prospects for developing more complex and robust quantum computation schemes based on molecular spin qubits. |
Thursday, March 7, 2019 12:27PM - 1:03PM |
S36.00003: Multifrequency and Chemical Tuning Studies of V(IV) Quantum Spins Invited Speaker: Joseph Zadrozny Complexes of the magnetic ion vanadium(IV) are at the frontier of molecular qubit research. Indeed, several recent investigations demonstrate that these ions are capable of spin relaxation times comparable to diamond’s nitrogen vacancy centers. In light of these exciting results, significant fundamental knowledge is still needed to further design these ions as qubits. For example, understanding the frequency dependence of V(IV) electron paramagnetic resonance properties underlies many applications, yet EPR studies are largely focused at only one frequency, X-band. Separately, understanding how ligand chemical composition affects spin relaxation times would enable the further improvement of relaxation times. Yet, the majority of research in this area is focused on vanadium ions surrounded by ligands that are composed entirely of carbon, oxygen, and sulfur. In this presentation, results from multi-frequency EPR analyses on families of vanadium(IV) complexes will be presented, with an eye toward the foregoing fundamental insight. |
Thursday, March 7, 2019 1:03PM - 1:39PM |
S36.00004: Operating quantum states in single magnetic molecules Invited Speaker: Wolfgang Wernsdorfer The endeavour of quantum electronics is driven by one of the most ambitious technological goals of today’s scientists: the realization of an operational quantum computer. We have started to address this goal by the new research field of molecular quantum spintronics, which combines the concepts of spintronics, molecular electronics and quantum computing. The building blocks are magnetic molecules, i.e. well-defined spin qubits. Various research groups are currently developing low-temperature scanning tunnelling microscopes to manipulate spins in single molecules, while others are working on molecular devices (such as molecular spin-transistors) to read and manipulate the spin state and perform basic quantum operations. We will present our recent measurements of geometric phases, the iSWAP quantum gate, the coherence time of a multi-state superposition, and the application to Grover’s algorithm [1-5]. |
Thursday, March 7, 2019 1:39PM - 2:15PM |
S36.00005: Magnetic relaxation dynamics in dysprosium complexes Invited Speaker: Nicholas Chilton Following our discovery of the first dysprosium metallocenium cation, [Dy(Cpttt)2][B(C6F5)4], which is the vanguard of the new generation of high-temperature single-molecule magnets,1 we have been investigating the magnetic relaxation dynamics of various dysprosium-based single-molecule magnets (SMMs) by experimental and theoretical techniques.2,3 Here we present our recent results in unravelling the competing magnetic relaxation processes, and offer some insights into the origin of the previously pervasive quantum tunneling of the magnetization in high-barrier dysprosium(III) SMMs. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700