Top 10 similar words or synonyms for flux_qubit
flux_qubits 0.599326
transresistance 0.598857
delta_sigma_modulation 0.596193
superconducting_quantum 0.593126
mesfet 0.589519
mach_zehnder_interferometer 0.586635
ćuk_converter 0.578509
varactor_diodes 0.575682
transimpedance_amplifier 0.574214
nanophotonic 0.567424
Top 30 analogous words or synonyms for flux_qubit
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Flux qubit | In quantum computing, and more specifically in superconducting quantum computing, flux qubits (also known as persistent current qubits) are micrometer sized loops of superconducting metal interrupted by a number of Josephson junctions. The junction parameters are engineered during fabrication so that a persistent current will flow continuously when an external magnetic flux is applied. As only an integer number of flux quantum is allowed to penetrate the superconducting ring, clockwise or counter-clockwise currents are developed in the loop to compensate (screen or enhance) a non-integer external flux bias. When the applied flux through the loop area is close to a half integer number of flux quanta, the two lowest energy eigenstates of the loop will be a quantum superposition of the clockwise and counter-clockwise currents. The two lowest energy eigenstates differ only by the relative quantum phase between the composing current-direction states. Higher energy eigenstates correspond to much larger persistent currents, that induce an additional flux quantum to the qubit loop, thus are well separated energetically from the lowest two eigenstates. This separation, known as the "qubit non linearity" criteria, allows operations with the two lowest eigenstates only, effectively creating a two level system. Usually, the two lowest eigenstates will serve as the computational basis for the logical qubit. |
Flux qubit | Coupling between two or more qubits is essential to implement many-qubit gates. The two basic coupling mechanisms are the direct inductive coupling and coupling via a microwave resonator. In the direct coupling, the circulating currents of the qubits inductively affect one another - clockwise current in one qubit induces counter-clockwise current in the other. In the Pauli Matrices formalism, a term appears in the Hamiltonian, essential for the controlled NOT gate implementation. The direct coupling might be further enhanced by kinetic inductance, if the qubit loops are made to share an edge, so that the currents will flow through the same superconducting line. Inserting a Josephson junction on that joint line will add a Josephson inductance term, and increase the coupling even more. To implement a switchable coupling in the direct coupling mechanism, as required to implement a gate of finite duration, an intermediate coupling loop may be used. The control magnetic flux applied to the coupler loop switches the coupling on and off, as implented, for example, in the D-Wave Systems machines. The second method of coupling utilizes an intermediate microwave cavity resonator, commonly implemented in a coplanar waveguide geometry. By tuning the energy separation of the qubits to match the one of the resonator, the phases of the loop currents are synchronized, and a coupling is implemented. Tuning the qubits in and out of resonance (for example, by modifying their bias magnetic flux) controls the duration of the gate operation. |
Flux qubit | Prof. Mooij's group at Delft in the Netherlands, along with collaborators, has pioneered flux qubit technology, and were the first to conceive, propose and implement flux qubits as they are known today. The Delft read-out scheme is based on a SQUID loop that is inductively coupled to the qubit, the qubit's state influences the critical current of the SQUID. The critical current can then be read-out using ramped measurement currents through the SQUID. Recently the group has used the plasma frequency of the SQUID as the read-out variable. |
Flux qubit | Dr. Il'ichev's group at IPHT Jena in Germany are using impedance measurement techniques based on the flux qubit influencing the resonant properties of a high quality tank circuit, which, like the Delft group is also inductively coupled to the qubit. In this scheme the qubit's magnetic susceptibility, which is defined by its state, changes the phase angle between the current and voltage when a small A.C. signal is passed into the tank circuit. |
Flux qubit | Recently Prof. Petrashov's group at Royal Holloway are using an Andreev interferometer probe to read out flux qubits. This read-out uses the phase influence of a superconductor on the conductance properties of a normal metal. A length of normal metal is connected at either end to either side of the qubit using superconducting leads, the phase across the qubit, which is defined by its state, is translated into the normal metal, the resistance of which is then read-out using low noise resistance measurements. |
Flux qubit | The flux qubit is distinguished from other types of superconducting qubit such as the charge qubit or phase qubit by the coupling energy and charging energy of its junctions. In the charge qubit regime the charging energy of the junctions dominates the coupling energy, while in a flux qubit the situation is reversed and the coupling energy dominates. Typically in a flux qubit the coupling energy is 10-100 times greater than the charging energy. It is this ratio that allows the Cooper pairs to flow continuously around the loop, rather than tunnel discretely across the junctions as in a charge qubit. |
Phase qubit | In quantum computing, and more specifically in superconducting quantum computing, the phase qubit is a superconducting device based on the superconductor-insulator-superconductor (SIS) Josephson junction, designed to operate as a quantum bit, or qubit. The phase qubit is closely related, yet distinct from, the flux qubit and the charge qubit, which are also quantum bits implemented by superconducting devices. |
Superconducting quantum computing | Architecture-specific readout (measurement) mechanisms exist. The readout of a phase qubit is explained in the qubit archetypes table above. A state of the flux qubit is often read by an adjust DC-SQUID magnetometer. A more general readout scheme includes a coupling to a microwave resonator, where the resonance frequency of the resonator is shifted by the qubit state. |
Kinetic inductance | Kinetic inductance is also used in a design parameter for superconducting flux qubits: formula_30 is the ratio of the kinetic inductance of the Josephson junctions in the qubit to the geometrical inductance of the flux qubit. A design with a low beta behaves more like a simple inductive loop, while a design with a high beta is dominated by the Josephson junctions and has more hysteretic behavior. |