Quantum gate device
|発明の名称 （英語）||Quantum gate device|
|発明の概要（英語）||This quantum gate device 10 comprises a first superconducting circuit 11 that resonates at a first resonance frequency, a second superconducting circuit 12 that resonates at a second resonance frequency, and a connection part 13 that connects the first and second superconducting circuits 11 and 12. The first superconducting circuit 11 comprises a first Josephson element 111, a second Josephson element group 112, and a first capacitor 114. The second Josephson element group 112 is formed by connecting n Josephson elements in series to a wiring made of a superconductor, and the Josephson energy possessed by each of the n Josephson elements is n times larger than that of the first Josephson element 11. A first wiring 115 forms a partial superconducting circuit 113 by connecting the first Josephson element 111 and the second Josephson element group 112 in an annular shape, and further connects the partial superconducting circuit 113 and the first capacitor 144 in parallel to each other. The quantum gate device 10 further has: a magnetic field application unit 14 that applies a static magnetic field into the partial superconducting circuit 113; and an electromagnetic wave irradiation unit (first electromagnetic wave irradiation unit 151) that irradiates the first superconducting circuit 11 and/or the second superconducting circuit 12 with an electromagnetic wave having a difference frequency corresponding to a difference between the first resonance frequency and the second resonance frequency.|
Background of the Invention]
The present invention relates to a quantum gate device as a constituent element of a quantum computer.
, Research and development of quantum computers have prevailed in recent years. The data expressed as either of 2 values (generally " 0 " and " 1 " ) will be calculated as a minimum unit in a conventional computer, With respect to this, in a quantum computer, it is expected that the computational power will become high by calculating as a minimum unit the overlapping states of 2 states processed quantitatively and mechanically,.
In a conventional computer, an operation called a logic gate is performed, i. e.,, inputs data and logic products (AND), logic and ( OR ), logic non-( NOT ), etc. logic operations are performed, and the results are output. The operation called quantum gate is similarly performed in quantum computer, inputs the data to perform a given logic operation to output the results. The device performing this operation is referred to as a quantum gate device. In a quantum gate arrangement, as a prerequisite for realizing overlapping states of 2 states, 2 states must be selectively taken from among the plurality of states that are mechanically discretized from 2 states (other than the 2 states).
In Non-Patent Document 1, a circuit called superconducting quantum cell ( transmon ) is described as a constituent element of a quantum gate device. The superconducting quantum cell is a circuit of 1 Joseph elements ( Josephson device ) and 1 capacitors connected in a loop using a wiring made of superconductors. Here, Joseph elements are made by holding 2 superconductors in a thin film made of an insulator.
If the quantum gate device is cooled to a temperature at which the Joseph element and the superconductor of the wiring become superconducting, current is passed through the Joseph element by Joseph effect within the superconducting quantum cell. Thus, superconducting quantum cells function as resonant circuits, which take any of the plurality of energy states after discretization by quantum mechanics,. A plurality of energy states are arranged at unequal intervals by the presence of Joseph elements, within the resonant circuit. Thus, If an electromagnetic wave having an energy corresponding to a minimum interval is incident on the Joseph element, then the superconducting quantum bit element may selectively take only 2 of the base state and 1 excitation states (and again, in a circuit in which the Joseph element is removed from the superconducting quantum bit element, a plurality of energy states are arranged at equal intervals, and if an electromagnetic wave having an energy corresponding to the interval is incident, more than 3 energy states) are taken. This would constitute a quantum gate device by taking only a plurality of combinations of superconducting quantum bits of 2 energy states, or by combining 1 or more superconducting quantum bits with other circuits,. [Prior Art Document ] [Non-Patent Document]
[Non-patent Document 1 ] J. Koch and Other 9 , " Charge insensitive qubit design derived from the Cooper pair box " , Physical Review A , (American ) , American Society of Physics issue , 2007 10 12, Volume 76, Paper No.042319
1. A quantum gate device, characterized by a : a ) th 1 superconducting circuit, having : a - 1 ) 1 th 1 Joseph elements ; a - 2 ) th 2 Joseph element groups, which connect n Joseph elements in series using a wiring made of superconductors, And each of the n Joseph elements has Joseph energy n times greater than Joseph energy of the 1 th Joseph element ; a - 3 ) th 1 capacitor; and a - 4 ) th 1 wiring, which forms a local superconducting circuit, by circularly connecting the 1 th Joseph element with the 2 th 2 Joseph element group and connecting the local superconducting circuit in parallel with the 1 th 1 capacitor, And composed of superconductors; and the 1 th superconducting circuit resonates at the 1 th resonant frequency ; b ) th 2 superconducting circuit, which has at least 1 Joseph elements, th 2 capacitor, th 2 wiring, which is composed of superconductors and resonates at the 2 th resonant frequency ; c ) connecting part, which has connecting part capacitors and th 3 wiring, which is respectively connected to the two poles of the connecting part capacitors and is composed of superconductors. And connecting said 1 th superconducting circuit to said 2 th superconducting circuit ; d ) magnetic field applying section, which applies a static magnetic field; to said local superconducting circuit and e ) electromagnetic wave irradiating section, which irradiates electromagnetic waves having a difference between said 1 th resonance frequency and said 2 th resonance frequency, i. e., a difference frequency, to said 1 th superconducting circuit.
2. The quantum gate device, as claimed in claim 1 wherein, said 2 th superconducting circuit is a superconducting quantum bit element formed by circularly connecting 1 Joseph elements and 1 th 2 capacitors by said 2 th distribution line.
3. The quantum gate device, as claimed in claim 1 or 2 wherein, said 1 th Joseph element is made of 2 superconductors holding a junction having a 1 th thin film formed of an insulator, Each of the Joseph elements constituting said 2 th group of Joseph elements is held by 2 superconductors with the junction of the 2 th film made of the same kind of insulator as said 1 th film, the value of the tunnel resistance in said 1 th group of Joseph elements is n times greater than the value of the tunnel resistance in each Joseph element constituting said 2 th group of Joseph elements.
4. The quantum gate apparatus as claimed in any one of claims 1 to 3, which is further provided with a: residual interaction eliminating electromagnetic wave irradiation section, which irradiates the electromagnetic wave, i. e. residual interaction eliminating electromagnetic wave; and irradiating adjusting section, which inverts the phase of the quantum bit cells to the aforementioned 1 th superconducting circuit. It performs irradiation of electromagnetic waves using said electromagnetic wave irradiating portion, and thereafter,, at a given time interval, 2 times to eliminate the residual interaction of the electromagnetic wave irradiating portion using said residual interaction to eliminate the irradiation of electromagnetic waves, and adjust the irradiation timing of the electromagnetic wave irradiating portion and the residual interaction to eliminate the electromagnetic wave irradiating portion in this manner.
5. The quantum gate apparatus, as claimed in claim 4 wherein, said residual interaction eliminating electromagnetic wave irradiating portion is constituted by the same means as said electromagnetic wave irradiating portion.
6. A bulk subcircuit, having a plurality of quantum gate devices as claimed in any one of claims 1 to 5.
|参考情報 （研究プロジェクト等）||ERATO NAKAMURA Macroscopic Quantum Machines AREA|
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