Molecular nanomagnets are zero-dimensional spin systems that exhibit quantum-mechanical behavior at low temperatures. Exploiting quantum-information theoretic measures, we quantify here the size of linear superpositions that can be generated within the ground multiplet of high- and low-spin nanomagnets. Amongst the former class of systems, we mainly focus on Mn ${}_{12}$ and Fe ${}_{8}$ . General criteria for maximizing such measures are also outlined, and illustrated with reference to spin clusters of different geometries. The actual character (micro or macroscopic) of linear superpositions in low-spin systems is inherently ill-defined. Here, this issue is addressed with specific reference to the Cr ${}_{7}$ Ni and V ${}_{15}$ molecules, characterized by an $S=1/2$ ground state. In both cases, the measures we obtain are larger than those of a single $s=1/2$ spin but not proportionate to the number and value of the constituent spins.Molecular nanomagnets are zero-dimensional spin systems that exhibit quantum-mechanical behavior at low temperatures. Exploiting quantum-information theoretic measures, we quantify here the size of linear superpositions that can be generated within the ground multiplet of high- and low-spin nanomagnets. Amongst the former class of systems, we mainly focus on Mn${}_{12}$ and Fe${}_{8}$. General criteria for maximizing such measures are also outlined, and illustrated with reference to spin clusters of different geometries. The actual character (micro or macroscopic) of linear superpositions in low-spin systems is inherently ill-defined. Here, this issue is addressed with specific reference to the Cr${}_{7}$Ni and V${}_{15}$ molecules, characterized by an $S=1/2$ ground state. In both cases, the measures we obtain are larger than those of a single $s=1/2$ spin but not proportionate to the number and value of the constituent spins.

arXiv:1304.7618Physical Review BSep 10, 20137 citations

Quantum Relaxation of Ensembles of Nanomagnets

Nikolay V. Prokof'ev, Philip C. E. Stamp

arXiv:cond-mat/9810354Journal of Low Temperature PhysicsDec 1, 199827 citations

On the Use of Classical and Quantum Fisher Information in Molecular Magnetism

Filippo Troiani

The present paper discusses the use of two information-theoretical quantities—namely, the classical and quantum Fisher information—in the context of molecular magnetism. These functions quantify the suitability of a given observable to the estimation of a physical parameter and provide the highest precision allowed by quantum mechanics in such an estimation process. The quantum Fisher information also quantifies the degree of macroscopicity of a quantum state. As illustrative examples of such applications, we compute the classical and quantum Fisher information of the Fe 4 molecular nanomagnet, used as a probe of an applied magnetic field or as a platform for generating Schrödinger cat states.The present paper discusses the use of two information-theoretical quantities—namely, the classical and quantum Fisher information—in the context of molecular magnetism. These functions quantify the suitability of a given observable to the estimation of a physical parameter and provide the highest precision allowed by quantum mechanics in such an estimation process. The quantum Fisher information also quantifies the degree of macroscopicity of a quantum state. As illustrative examples of such applications, we compute the classical and quantum Fisher information of the Fe 4 molecular nanomagnet, used as a probe of an applied magnetic field or as a platform for generating Schrödinger cat states.

MagnetochemistrySep 8, 20162 citations

Size dependence of strong coupling between nanomagnets and photonic cavities

Öney O. Soykal, Michael E. Flatté

The coherent dynamics of a coupled photonic cavity and a nanomagnet is explored as a function of nanomagnet size. For sufficiently strong coupling eigenstates involving highly entangled photon and spin states are found, which can be combined to create coherent states. As the size of the nanomagnet increases its coupling to the photonic mode also monotonically increases, as well as the number of photon and spin states involved in the system's eigenstates. For small nanomagnets the crystalline anisotropy of the magnet strongly localizes the eigenstates in photon and spin number, quenching the potential for coherent states. For a sufficiently large nanomagnet the macrospin approximation breaks down and different domains of the nanomagnet may couple separately to the photonic mode. Thus the optimal nanomagnet size is just below the threshold for failure of the macrospin approximation.The coherent dynamics of a coupled photonic cavity and a nanomagnet is explored as a function of nanomagnet size. For sufficiently strong coupling eigenstates involving highly entangled photon and spin states are found, which can be combined to create coherent states. As the size of the nanomagnet increases its coupling to the photonic mode also monotonically increases, as well as the number of photon and spin states involved in the system's eigenstates. For small nanomagnets the crystalline anisotropy of the magnet strongly localizes the eigenstates in photon and spin number, quenching the potential for coherent states. For a sufficiently large nanomagnet the macrospin approximation breaks down and different domains of the nanomagnet may couple separately to the photonic mode. Thus the optimal nanomagnet size is just below the threshold for failure of the macrospin approximation.

arXiv:1005.3068Physical Review BSep 10, 201086 citations

{}_{12}

and Fe

{}_{8}

. General criteria for maximizing such measures are also outlined, and illustrated with reference to spin clusters of different geometries. The actual character (micro or macroscopic) of linear superpositions in low-spin systems is inherently ill-defined. Here, this issue is addressed with specific reference to the Cr

{}_{7}

Ni and V

{}_{15}

molecules, characterized by an

S=1/2

ground state. In both cases, the measures we obtain are larger than those of a single

s=1/2

spin but not proportionate to the number and value of the constituent spins.