The Holstein-Primakoff transformation is generalized to develop a quantum flavor wave theory for spin systems with orbital degeneracy. Elementary excitations of ordered ground states consist of spin, orbital , and spinorbital waves. Spin and spin-orbital waves couple to each other due to orbital anisotropy and Hund’s rule, resulting in new modes observable by inelastic neutron scattering. In th...

Circuit QED on a chip has become a powerful platform for simulating complex many-body physics. In this report, we realize a Dicke-Ising model with an antiferromagnetic nearest-neighbor spin-spin interaction in circuit QED with a superconducting qubit array. We show that this system exhibits a competition between the collective spin-photon interaction and the antiferromagnetic nearest-neighbor s...

I review recent work, performed in collaboration primarily with N. Read and Jinwu Ye, on the properties of quantum antiferromagnets in two dimensions. The emphasis is on the properties of the antiferromagnet in states which do not have any long-range magnetic order. The universal spin dynamics in the quantum critical region of number of frustrated and random antiferromagnets is studied; implica...

Advances in the semiconductor technologies allow the realization of quantum dot structure in which a finite number of electrons are confined by an artificial potentials [1–3]. The number of electrons in a quantum dot, denoted N , which can also be controlled experimentally, affects many physical properties of the quantum dot. By changing the quantum dot size and the number of electrons, far-inf...

Consider a generic quantum spin chain that can be mapped to free quadratic fermions via Jordan-Wigner (JW) transformation. In the presence of arbitrary boundary magnetic fields, this Hamiltonian is no longer after JW Using ancillary sites and enlarging we first introduce bigger Hamiltonian. Then diagonalize enlarged in its most form show all states are degenerate because zero mode. The eigensta...

Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We intro...

The perturbation theory is developed based on small parameters which naturally appear in solid state quantum computation. We report the simulations of the dynamics of quantum logic operations with a large number of qubits (up to 1000). A nuclear spin chain is considered in which selective excitations of spins are provided by having a uniform gradient of the external magnetic field. Quantum logi...

Magnetic semiconductor quantum dots with a few carriers represent an interesting model system where ferromagnetic interactions can be tuned by voltage. By designing the geometry of a doped quantum dot, one can tailor the anisotropic quantum states of magnetic polarons. The strong anisotropy of magnetic polaron states in disklike quantum dots with holes comes from the spin splitting in the valen...

Landé factor Happ applied magnetic field (vector) Happ applied magnetic field (magnitude) Hm molecular field J exchange integral J total angular momentum k0 propagation vector l orbital quantum number l orbital momentum L orbital momentum L Langevin function m magnetic quantum number m0 measured magnetic moment at 0 K m magnetic moment ml orbital moment ms spin moment mz projection of m along H...

The last decade has witnessed substantial interest in protocols for transferring information on networks of quantum mechanical objects. A variety of control methods and network topologies have been proposed, on the basis that transfer with perfect fidelity-i.e., deterministic and without information loss-is impossible through unmodulated spin chains with more than a few particles. Solving the o...