Abstract: The disclosure is directed to devices, systems, and methods for a generation of a decoherence-protected subspace in a quantum system. The decoherence-protected subspace provides the quantum system with reduced sensitivity to environmental magnetic, electric, and thermal noises. Quantum information operation based on the quantum system can be performed while this decoherence-protected subspace is maintained.

Abstract: A molecular-spin qubit is formed from a coordination complex having a plurality of strong-field ligands bound to a metal-atom center. The ground state has non-zero spin, and the resulting ground-state magnetic sublevels are separated by microwave or millimeter-wave frequencies, even in the absence of an external field. Two of these sublevels may be used as a quantum resource for quantum information processing, quantum communication, quantum memory, sensing, and other applications. Optical pumping to an excited state may be used to spin-polarize the molecular-spin qubit, and to measure its population by detecting photoluminescence. The energy-level structure of the metal-atom center can be modified due to its interaction with the ligands, therefore allowing the molecular-spin qubit to be “chemically tuned” based on the number and type of ligands. Ensembles of these molecular-spin qubits can be controllably deposited on a surface, or otherwise integrated into devices and structures.

Abstract: This disclosure relates to optical devices for quantum information processing applications. In one example implementation, a semiconductor structure is provided. The semiconductor structure may be embedded with single defects that can be individually addressed. An electric bias and/or one or more optical excitations may be configured to control the single defects in the semiconductor structure to produce single photons for use in quantum information processing. The electric bias and optical excitations are selected and adjusted to control various carrier processes and to reduce environmental charge instability of the single defects to achieve optical emission with wide wavelength tunability and narrow spectral linewidth. Electrically controlled single photon source and other electro-optical devices may be achieved.

Abstract: The disclosure is directed to devices, systems, and methods for performing quantum state-mediated microwave-to-optical energy conversion. Such quantum state-mediated energy conversion may be achieved via coherent interactions between an optical excitation and microwave electric field mediated by various quantum states in a defect embedded in a crystalline lattice. Such energy conversion enables coherent electro-optical modulation of optical emission from the defect, microwave-optical transduction, optical detection of microwave, and optical frequency mixing in the optical emission from the defect. The optical emission from the defect maintains and carries quantum coherence in the defect. Such devices and methods may be applied in quantum information processing systems.

Abstract: A method for creating a logic state for teleporting quantum information using a single photon is described. The method includes receiving a photon with an initial polarization and causing a first semiconductor crystal to have a first spin orientation. The photon interacts with the first semiconductor crystal for producing a resulting polarization dependent upon the first spin orientation. Causing the photon to interact with the first semiconductor crystal generates a maximally entangled state.

Abstract: Ferromagnetic semiconductor-based compositions, systems and methods that enable studies of the dynamics and magnetoresistance of individual magnetic domain walls, and which provide enhanced magnetic switching effects relative to metallic ferromagnets. Aspects of the present invention are enabled by recent studies of the Giant Planar Hall effect (GPHE), and in particular GPHE in (Ga,Mn)As—based devices. The GPHE generally originates from macro- and micromagnetic phenomena involving single domain reversals. The GPHE-induced resistance change in multiterminal, micron-scale structures patterned from (Ga,Mn)As can be as large as about 100?, four orders of magnitude greater than analogous effects previously observed in metallic ferromagnets. Accordingly, recent data provide sufficient resolution to enable real-time observations of the nucleation and field-induced propagation of individual magnetic domain walls within such monocrystalline devices.

Abstract: Ferromagnetic semiconductor-based compositions, systems and methods that enable studies of the dynamics and magnetoresistance of individual magnetic domain walls, and which provide enhanced magnetic switching effects relative to metallic ferromagnets. Aspects of the present invention are enabled by recent studies of the Giant Planar Hall effect (GPHE), and in particular GPHE in (Ga,Mn)As-based devices. The GPHE generally originates from macro- and micromagnetic phenomena involving single domain reversals. The GPHE-induced resistance change in multiterminal, micron-scale structures patterned from (Ga,Mn)As can be as large as about 100&OHgr;, four orders of magnitude greater than analogous effects previously observed in metallic ferromagnets. Accordingly, recent data provide sufficient resolution to enable real-time observations of the nucleation and field-induced propagation of individual magnetic domain walls within such monocrystalline devices.

Abstract: Submicron ferromagnets, of selected size and spacing, are introduced into semiconductor by means of ion implantation and subsequent heat treatments. The resulting semiconductor contains ferromagnets at high density and which exhibit Curie temperatures exceeding room temperature. The semiconductor retains its intrinsic physical properties, such as optical and transport properties, after incorporation of the ferromagnetic nanostructures.