University of Seoul Industry Cooperation Foundation (Seoul, KR) Doyeol Ahn garnered U.S. Patent 7,655,850 for universal quantum gates that includes single qubit and two-qubit gates.
Quantum computing utilizes quantum particles to carry out computational processes. The fundamental unit of quantum information is called a quantum bit or qubit. Semiconductor implementation of quantum bits and quantum gates is of current technological interest for scalable quantum computation.
A universal quantum gate includes a single qubit gate including aquantum dot, the quantum dot to include a qubit. The qubit, for example, may be represented by a state from among polarized intervalley states of an electron in the quantum dot. The universal quantum gate further includes a two-qubit gate coupled to the single qubit gate. The two-qubit gate, for example, includes a first quantum dot and a second quantum dot. The first quantum dot, for example, to include a first qubit, the first qubit may be represented by a state from among polarized intervalley states of an electron in the first quantum dot. The second quantum dot, for example, to include a second qubit, the second qubit may be represented by a state from among polarized intervalley states of an electron in the second quantumdot.
Gate voltages, for example, may be applied to the first quantum dot and the second quantum dot. These gate voltages, for example, may be adjusted such that an energy level of the representative states of the first and second qubits is based on an integer multiple of an inter-dot Coulomb-energy level.
One of the most formidable challenges, among the stringent requirements for the implementation of solid-state qubit, may be minimizing decoherence effects on the fragile quantum states. Thus, current approaches for the solid state qubits are mostly based on the coherent quantum state of a nuclear spin of impurity atoms implanted on the surface of silicon (Si) and the electron spin confined in the quantum dots.
Recently, research and development in the implementation of spin based qubit have been substantial, which include the isolation of electron spin states in coupled quantum dots, coherent exchange of two spins in a double dot system, single electron spin evolution under a static magnetic field, and the realization of Rabi oscillation of a single electron spin.
Quantum gate operation of the spin qubits may utilize the Heisenberg interaction or the exchange interaction. It is well known that the Heisenberg interaction alone may not provide a universal quantum gate because it has too much symmetry. Moreover, in order to control the Heisenberg interaction in quantum dots, both static and dynamic magnetic fields are likely required. Therefore, implementation is needed such that a single physical state can possibly constitute one logical qubit with a universal gate operation that is substantially electrically controlled.
Quantum gate operation of the spin qubits may utilize the Heisenberg interaction or the exchange interaction. It is well known that the Heisenberg interaction alone may not provide a universal quantum gate because it has too much symmetry. Moreover, in order to control the Heisenberg interaction in quantum dots, both static and dynamic magnetic fields are likely required. Therefore, implementation is needed such that a single physical state can possibly constitute one logical qubit with a universal gate operation that is substantially electrically controlled.
FIG. 2 is a diagram showing an illustrative embodiment of a single qubit gate.
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