Ion-optical cavity coupling system and method
An ionic optical cavity coupling system and method are described. The system includes a first optical cavity, a second optical cavity, and an ion trap system including a direct current electrode pair, a grounding electrode pair, and a radio frequency electrode pair. At least one ion is arranged in the ion trap system. Furthermore, the first optical cavity is used for obtaining a quantum optical signal and sending the quantum optical signal to the ion trap system, so that quantum information of the quantum optical signal is transferred to a single ion in the ion trap system. The second optical cavity is used for obtaining quantum information in the single ion in the ion trap system.
1. An ion-optical cavity coupling system, comprising:
a first optical cavity,
a second optical cavity,
a direct current electrode pair,
a ground electrode pair, and
a radio frequency electrode pair, wherein
the ion-optical cavity coupling system comprises at least one ion;
two optical cavity mirrors of the first optical cavity are distributed on two sides of the at least one ion, two optical cavity mirrors of the second optical cavity are distributed between the two optical cavity mirrors of the first optical cavity, and a beam waist radius of the first optical cavity is greater than a beam waist radius of the second optical cavity;
two direct current electrodes of the direct current electrode pair are distributed on outer sides of the two optical cavity mirrors of the first optical cavity, and the ground electrode pair and the radio frequency electrode pair are distributed between the two optical cavity mirrors of the first optical cavity;
the first optical cavity obtains a quantum optical signal, and transfers quantum information of the quantum optical signal to a single ion of the ion-optical cavity coupling system; and
the second optical cavity obtains the quantum information in the single ion.
2. The system according to claim 1 , wherein that the first optical cavity obtains the quantum optical signal, and transfers quantum information of the quantum optical signal to the single ion of the ion-optical cavity coupling system comprises:
the first optical cavity obtains the quantum optical signal to enable the quantum optical signal to be absorbed by the at least one ion; and sequentially transfers the quantum information of the quantum optical signal to a collective excited state and an excited state of a collective motion mode of the at least one ion, and transfers the quantum information of the quantum optical signal from the excited state of the collective motion mode to an excited state of one of the at least one ion.
3. The system according to claim 1 , wherein that the second optical cavity obtains the quantum information in the single ion comprises:
the second optical cavity positions the single ion using laser light to obtain the quantum information in the single ion.
4. The system according to claim 1 , wherein both a strength of coupling between the first optical cavity and any one of the at least one ion, and a strength of coupling between the second optical cavity and any one of the at least one ion, are represented by g 0 , and wherein g 0 is expressed by the following formula:
g
0
=
3
c
γ
λ
2
π
2
L
ω
0
2
wherein c represents a speed of light, L represents a length of the first optical cavity or the second optical cavity, ω 0 represents a beam waist radius of the first optical cavity or the second optical cavity, λ represents a wavelength of the quantum optical signal, and γ represents a spontaneous emission rate of an ion.
5. The system according to claim 4 , wherein a total coupling strength g N of all ions in the ion-optical cavity coupling system is expressed by the following formula:
g N =√{square root over (N)}g 0
wherein N represents a total quantity of ions in the ion-optical cavity coupling system.
6. The system according to claim 1 , wherein both a first optical cavity mirror of the first optical cavity and a first optical cavity mirror of the second optical cavity are coated with a first reflection film, both a second optical cavity mirror of the first optical cavity and a second optical cavity mirror of the second optical cavity are coated with a second reflection film, a reflectivity of the first reflection film falls within a first preset range, a reflectivity of the second reflection film falls within a second preset range, and a maximum value of the first preset range is less than a minimum value of the second preset range.
7. The system according to claim 1 , wherein when a quantity of the at least one ion is 1, distances between the two optical cavity mirrors of the second optical cavity and an equilibrium position of the ion are the same, and two ground electrodes of the ground electrode pair and two radio frequency electrodes of the radio frequency electrode pair are distributed on two sides of the ion.
8. The system according to claim 1 , wherein when a quantity of the at least one ion is greater than 1, a straight line on which an equilibrium position of the at least one ion is located is a center line, distances between the two optical cavity mirrors of the second optical cavity and the center line are the same.
9. The system according to claim 8 , wherein there is an included angle between a ground electrode of the ground electrode pair and an adjacent radio frequency electrode, and the included angle is greater than 0 degrees and less than 180 degrees; and
one optical cavity mirror of the second optical cavity is located in the included angle between the ground electrode and the adjacent radio frequency electrode, and the other optical cavity mirror of the second optical cavity is located in an included angle between the other ground electrode and the other adjacent radio frequency electrode.
10. The system according to claim 1 , wherein when a quantity of the at least one ion is greater than 1, the beam waist radius of the first optical cavity is greater than a spacing between two adjacent ions, and the beam waist radius of the second optical cavity is less than or equal to the spacing between two adjacent ions.
11. An ion-optical cavity coupling method, wherein the method is performed with an ion-optical cavity coupling system that comprises: a first optical cavity, a second optical cavity, a direct current electrode pair, a ground electrode pair, and a radio frequency electrode pair, wherein the ion-optical cavity coupling system comprises at least one ion; two optical cavity mirrors of the first optical cavity are distributed on two sides of the at least one ion, two optical cavity mirrors of the second optical cavity are distributed between the two optical cavity mirrors of the first optical cavity, wherein a beam waist radius of the first optical cavity is greater than a beam waist radius of the second optical cavity; two direct current electrodes of the direct current electrode pair are distributed on outer sides of the two optical cavity mirrors of the first optical cavity, and the ground electrode pair and the radio frequency electrode pair are distributed between the two optical cavity mirrors of the first optical cavity; and wherein the method comprises:
obtaining, using the first optical cavity, a quantum optical signal that carries quantum information;
transferring the quantum information of the quantum optical signal to a single ion of the ion-optical cavity coupling system using the first optical cavity; and
obtaining the quantum information in the single ion using the second optical cavity.
12. The method according to claim 11 , wherein the transferring the quantum information of the quantum optical signal to the single ion of the ion-optical cavity coupling system using the first optical cavity comprises:
enabling the quantum optical signal to be absorbed by the at least one ion under a confinement effect produced by the three electrode pairs and using the first optical cavity; and sequentially transferring the quantum information of the quantum optical signal to a collective excited state and an excited state of a collective motion mode of the at least one ion, and transferring the quantum information of the quantum optical signal from the excited state of the collective motion mode to an excited state of one of the at least one ion.
13. The method according to claim 11 , wherein the obtaining the quantum information in the single ion using the second optical cavity comprises:
positioning the single ion using laser light and the second optical cavity; and
obtaining the quantum information in the single ion using the second optical cavity.
14. The method according to claim 11 , wherein both a strength of coupling between the first optical cavity and any one of the at least one ion, and a strength of coupling between the second optical cavity and any one of the at least one ion, are represented by g 0 , and wherein g 0 is expressed by the following formula:
g
0
=
3
c
γ
λ
2
π
2
L
ω
0
2
wherein c represents a speed of light, L represents a length of the first optical cavity or the second optical cavity, ω 0 represents a beam waist radius of the first optical cavity or the second optical cavity, λ represents a wavelength of the quantum optical signal, and γ represents a spontaneous emission rate of an ion.
15. The method according to claim 14 , wherein a total coupling strength g N of all ions in the ion-optical cavity coupling system is expressed by the following formula:
g N =√{square root over (N)}g 0
wherein N represents a total quantity of ions in the ion-optical cavity coupling system.
16. The method according to claim 11 , wherein both a first optical cavity mirror of the first optical cavity and a first optical cavity mirror of the second optical cavity are coated with a first reflection film, both a second optical cavity mirror of the first optical cavity and a second optical cavity mirror of the second optical cavity are coated with a second reflection film, a reflectivity of the first reflection film falls within a first preset range, a reflectivity of the second reflection film falls within a second preset range, and a maximum value of the first preset range is less than a minimum value of the second preset range.
17. The method according to claim 11 , wherein when a quantity of the at least one ion is 1, distances between the two optical cavity mirrors of the second optical cavity and an equilibrium position of the ion are the same, and two ground electrodes of the ground electrode pair and two radio frequency electrodes of the radio frequency electrode pair are distributed on two sides of the ion.
18. The method according to claim 11 , wherein when a quantity of the at least one ion is greater than 1, a straight line on which an equilibrium position of the at least one ion is located is a center line, distances between the two optical cavity mirrors of the second optical cavity and the center line are the same.
19. The method according to claim 18 , wherein there is an included angle between a ground electrode of the ground electrode pair and an adjacent radio frequency electrode, and the included angle is greater than 0 degrees and less than 180 degrees; and
one optical cavity mirror of the second optical cavity is located in the included angle between the ground electrode and the adjacent radio frequency electrode, and the other optical cavity mirror of the second optical cavity is located in an included angle between the other ground electrode and the other adjacent radio frequency electrode.
20. The method according to claim 11 , wherein when a quantity of the at least one ion is greater than 1, the beam waist radius of the first optical cavity is greater than a spacing between two adjacent ions, and the beam waist radius of the second optical cavity is less than or equal to the spacing between two adjacent ions.