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Time-domain simulation of a universal quantum gate
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View: Figures


Image of FIG. 1.
FIG. 1.

Cross-sectional view of the quartic potential. The two dots, A and B, resemble two-dimensional harmonic oscillator potentials with . Each dot will contain a particle. The interaction of the particles is controlled by the parameter .

Image of FIG. 2.
FIG. 2.

Location of the localized magnetic sources relative to the dots. The particle in dot B is to be manipulated without disturbing the particle in dot A. and are the primarily sources. and are there to nullify the effect on dot A.

Image of FIG. 3.
FIG. 3.

Relative strengths of the magnetic fields resulting from the localized sources in Fig. 2.

Image of FIG. 4.
FIG. 4.

The Bloch sphere is a way of visualizing the state of a single qubit (Ref. 1). The expected value of the state of the qubit is calculated by the expected value of the operator .

Image of FIG. 5.
FIG. 5.

The time lapse of the wave functions during a CNOT transformation. The contour diagrams on the plane indicate the quartic potential of Fig. 1.

Image of FIG. 6.
FIG. 6.

Graph of the important parameters during the CNOT transformation. Particle I is the control particle, which does not change during the transformation. Particle II, the target particle, begins in the logical 1 state, indicated by at . The first step is the application of the field, which turns II around the axis to . At this point, the parameter , which controls the gating between the two particles, is lowered, and we begin to see some exchange energy at about . Since the control particle is , it is only the lower half of particle II that feels the exchange energy, causing the angle of particle II to precess around the axis. When it reaches at , a pulse turns it around the axis to the direction, i.e., a logical 0.

Image of FIG. 7.
FIG. 7.

Graph of the tunneling between the two particles during the CNOT transformation. The top plot is the parameter. The second plot illustrates the position of the two particles relative to center. The last two plots show the tunneling of particle I to dot B and particle II to dot A, respectively.

Image of FIG. 8.
FIG. 8.

Graph of the important parameters during a CNOT transformation, but with the control particle at , i.e., logical 0. The process parallels the one in Fig. 6, but since II is spin up, only the upper part of particle II feels the exchange and precesses in the opposite direction. The result is, particle II ends in , a logical 1.

Image of FIG. 9.
FIG. 9.

Time lapse of the wave functions during a one-particle Hadamard transformation. Notice that particle I is unaffected.

Image of FIG. 10.
FIG. 10.

The Hadamard transformation. Only particle II is manipulated by the fields.

Image of FIG. 11.
FIG. 11.

The phase transformation. Particle II is manipulated by the field. Particle I is unaffected because it is always up or down.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Time-domain simulation of a universal quantum gate