Amplitude modulated pulses for implementation of entangling gates in ion trap quantum computers
A method of performing an entangling gate operation using a quantum computer system includes configuring, by a classical computer, an amplitude function of an amplitude-modulated laser pulse over a plurality of time segments to cause entangling interaction between a pair of trapped ions of a plurality of trapped ions, each of the plurality of trapped ions having two frequency-separated states defining a qubit, where the amplitude function in each time segment is splined using a set of basis functions and associated control parameters, and performing an entangling gate operation between the pair of trapped ions by applying, by a system controller, an amplitude-modulated laser pulse having the configured amplitude function to the pair of trapped ions.
1. A method of performing an entangling gate operation using a quantum computer system, comprising:
configuring, by a classical computer, an amplitude function of an amplitude-modulated laser pulse over a plurality of time segments to cause entangling interaction between a pair of trapped ions of a plurality of trapped ions, each of the plurality of trapped ions having two frequency-separated states defining a qubit, wherein the amplitude function in each time segment is splined using a set of basis functions and associated control parameters; and
performing an entangling gate operation between the pair of trapped ions by applying, by a system controller, an amplitude-modulated laser pulse having the configured amplitude function to the pair of trapped ions.
2. The method according to claim 1 , wherein the performing of the entangling gate operation comprises modulating the laser pulse based on instructions provided from the classical computer.
3. The method according to claim 1 , wherein the set of basis functions comprises basis functions of a B-spline.
4. The method according to claim 1 , wherein the configuring of the amplitude function of the amplitude-modulated laser pulse comprises computing the associated control parameters based on a phase-space condition and an entangling angle condition.
5. The method according to claim 4 , wherein the computing of the associated control parameters is further based on a stabilization condition or a power-optimal condition.
6. The method according to claim 1 , wherein the system controller comprises an acousto-optic modulator, which is configured to selectively act on each of the ions of the pair of trapped ions.
7. A non-volatile computer-readable medium including computer program instructions, which when executed by a processor, cause the processor to:
configure an amplitude function of an amplitude-modulated laser pulse over a plurality of time segments to cause entangling interaction between a pair of trapped ions of a plurality of trapped ions, each of the plurality of trapped ions having two frequency-separated states defining a qubit, wherein the amplitude function in each time segment is splined using a set of basis functions and associated control parameters; and
perform an entangling gate operation between the pair of trapped ions by applying an amplitude-modulated laser pulse having the configured amplitude function to the pair of trapped ions.
8. The non-volatile computer-readable medium according to claim 7 , wherein the performing of the entangling gate operation comprises modulating the laser pulse, by a system controller, based on instructions provided from a classical computer.
9. The non-volatile computer-readable medium according to claim 7 , wherein the set of basis functions comprises basis functions of a B-spline.
10. The non-volatile computer-readable medium according to claim 7 , wherein the configuring of the amplitude function of the amplitude-modulated laser pulse comprises computing the associated control parameters based on a phase-space condition and an entangling angle condition.
11. The non-volatile computer-readable medium according to claim 10 , wherein the computing of the associated control parameters is further based on a condition of stabilization or a power-optimal condition.
12. A quantum computing system, comprising:
a plurality of trapped ions, each of the trapped ions having two hyperfine states defining a qubit; and
a classical computer comprising non-volatile memory having a number of instructions stored therein which, when executed by a processor, causes the quantum computing system to perform operations comprising:
configuring an amplitude function of an amplitude-modulated laser pulse over a plurality of time segments to cause entangling interaction between a pair of trapped ions of a plurality of trapped ions, each of the plurality of trapped ions having two frequency-separated states defining a qubit, wherein the amplitude function in each time segment is splined using a set of basis functions and associated control parameters; and
performing an entangling gate operation between the pair of trapped ions by applying, by a system controller, an amplitude-modulated laser pulse having the configured amplitude function to the pair of trapped ions.
13. The quantum computing system according to claim 12 , wherein the performing of the entangling gate operation comprises modulating the laser pulse based on instructions provided from the classical computer.
14. The quantum computing system according to claim 12 , wherein
each of the trapped ions is an ion having a nuclear spin and an electron spin such that a difference between the nuclear spin and the electron spin is zero.
15. The quantum computing system according to claim 14 , wherein
each of the trapped ions is an ion having a nuclear spin ½ and the 2 S 1/2 hyperfine states.
16. The quantum computing system according to claim 15 , wherein the ion is 171 Yb + .
17. The quantum computing system according to claim 15 , wherein the ion is 133 Ba + .
18. The quantum computing system according to claim 12 , wherein the set of basis functions comprises basis functions of a B-spline.
19. The quantum computing system according to claim 12 , the configuring of the amplitude function of the amplitude-modulated laser pulse comprises computing the associated control parameters based on a phase-space condition and an entangling angle condition.
20. The quantum computing system according to claim 19 , wherein the computing of the associated control parameters is further based on a stabilization condition or a power-optimal condition.
21. The quantum computing system according to claim 12 , further comprising:
an acousto-optic modulator, which is configured to selectively deliver the amplitude-modulated laser pulse to each of the plurality of trapped ions; and
a field-programmable gate array (FPGA) that is configured to receive instructions from the classical computer and transfer control signals, which is derived from the instructions received from the classical computer, to the acousto-optic modulator, wherein the transferred control signals provide information that enables the acousto-optic modulator to selectively deliver the amplitude-modulated laser pulse to each of the plurality of trapped ions.