Frequency management for quantum control

1. A system comprising:

a quantum control pulse generation circuit operable to generate a quantum control pulse; and

a multi-tone generation circuit operably coupled to the quantum control pulse generation circuit, wherein:

the multi-tone generation is operable to generate a plurality of fixed-frequency signals,

each of the plurality of fixed-frequency signals is at a different one of a plurality of frequencies from a first frequency to a second frequency,

any frequency, from the first frequency to the second frequency, can be achieved by tuning the quantum control pulse, and

frequency spacing between frequency-adjacent signals of the plurality of fixed-frequency signals is less than or equal to a range of frequencies over which the quantum control pulse generation circuit is operable to generate the quantum control pulse.

2. The system of claim 1 , wherein the quantum control pulse generation circuit is operable to:

generate a plurality of baseband pulses; and

upconvert the baseband pulses to an intermediate frequency to generate a plurality of quantum control pulses, wherein the intermediate frequency is tunable over a range at least as large as the frequency spacing.

3. The system of claim 1 , wherein:

the system comprises a quantum control interconnect circuit operably coupled to the quantum control pulse generation circuit and the multi-tone generator circuit, and

the quantum control interconnect circuit comprises one or more mixers operable to upconvert the quantum control pulse using one or more of the plurality of fixed-frequency signals; and

the quantum control interconnect circuit is operable to convey upconverted quantum control pulses from the one or more mixers to one or more qubits.

4. The system of claim 1 , wherein:

the system comprises a signal routing circuit that couples one or more output ports of the multi-tone generator circuit to one or more input ports of a quantum control interconnect circuit,

which one or more output ports of the multi-tone generator circuit is connected to which one or more input ports of the quantum control interconnect circuit is different for different configurations of the signal routing circuit.

5. The system of claim 4 , wherein which of the different configurations of the signal routing circuit is used is controllable via one or more digital control signals from the quantum control pulse generation circuit.

6. The system of claim 1 , wherein:

the system comprises a quantum control interconnect circuit operably coupled to the quantum control pulse generation circuit, and

the quantum control interconnect circuit comprises an upconverter operable to upconvert a readout pulse from the pulse generation circuit using a variable-frequency signal; and

the quantum control interconnect circuit is operable to convey the upconverted quantum readout pulse from the upconverter to a quantum element readout circuit.

7. The system of claim 6 , wherein:

the quantum control interconnect circuit comprises a downconverter operable to downconvert a return pulse from the quantum element readout circuit; and

the quantum control interconnect circuit is operable to convey the downconverted return pulse from the downconverter to the quantum control pulse generation circuit.

8. The system of claim 1 , wherein the multi-tone generator circuit comprises a crystal oscillator, a first signal processing circuit, a plurality of phase locked loops, and a plurality of resonator circuits wherein:

the crystal oscillator is configured to generate a first fixed-frequency intermediary signal;

the first signal processing circuit is configured to process the first fixed-frequency intermediary signal to generate a plurality of fixed-frequency intermediary signals;

a frequency of each of the plurality of fixed-frequency intermediary signals is an integer multiple of a frequency of the first fixed-frequency intermediary signal;

each of the plurality of phase locked loops is configured to receive a respective one of the plurality of fixed-frequency intermediary signals and receive an output of a respective one of the plurality of resonator circuits; and

each of the plurality of resonator circuits is configured to receive an output of a respective one of the plurality of phase locked loops.

9. The system of claim 8 , wherein one or more outputs of the plurality of resonator circuits are one or more of the plurality of fixed-frequency signals.

10. The system of claim 8 , wherein two or more outputs of the plurality of resonator circuits are mixed together to generate one or more of the plurality of fixed-frequency signals.

11. The system of claim 8 , wherein the processing of the first fixed-frequency intermediary signal by the first signal processing circuit does not use any voltage controlled oscillators.

12. The system of claim 8 , wherein the processing of the first fixed-frequency intermediary signal by the first signal processing circuit does not use any feedback loops.

13. The system of claim 8 , wherein the first signal processing circuit comprises one or more mixers, one or more amplifiers, one or more filters, one or more frequency multipliers and one or more splitters.

14. The system of claim 1 , wherein the multi-tone generator circuit comprises a crystal oscillator, a first signal processing circuit, a phase locked loop, a resonator circuit, and a second signal processing circuit wherein:

the crystal oscillator is configured to generate a first fixed-frequency intermediary signal;

the first signal processing circuit is configured to process the first fixed-frequency intermediary signal to generate a plurality of fixed-frequency intermediary signals;

a frequency of each of the plurality of fixed-frequency intermediary signals is an integer multiple of a frequency of the first fixed-frequency intermediary signal;

the phase locked loop is configured to receive one of the plurality of fixed-frequency intermediary signals and an output of the resonator circuit;

the resonator circuit is configured to receive an output of the phase locked loop; and

the second signal processing circuit is configured to mix an output of the resonator circuit and one or more of the plurality of fixed-frequency intermediary signals to generate one or more of the plurality of fixed-frequency signals.

15. The system of claim 14 , wherein a bandwidth of the phase locked loop is set such that phase noise of the plurality of fixed-frequency signals at offset frequencies below a first frequency is phase noise of the first signal processing circuit, and phase noise of the plurality of fixed-frequency signals at frequencies above a second frequency, higher than the first frequency, is phase noise of the resonator circuit.

16. The system of claim 14 , wherein the processing of the first fixed-frequency intermediary signal by the first signal processing circuit does not use any voltage controlled oscillators.

17. The system of claim 14 , wherein the processing of the first fixed-frequency intermediary signal by the first signal processing circuit does not use any feedback loops.

18. The system of claim 14 , wherein the first signal processing circuit comprises one or more mixers, one or more amplifiers, one or more filters, one or more frequency multipliers, and one or more splitters.

19. The system of claim 14 , wherein:

one or more of the plurality of fixed-frequency intermediary signals is coupled to one of a plurality of output ports of the quantum control interconnect circuit;

the output of the resonator circuit is coupled to one of the plurality of output ports of the quantum control interconnect circuit; and

one or more of the plurality of fixed-frequency signals are coupled to a respective one or more of the plurality of output ports of the quantum control interconnect circuit.

20. The system of claim 1 , wherein the multi-tone generator circuit comprises a crystal oscillator, and a first signal processing circuit, wherein:

the crystal oscillator is configured to generate the fixed-frequency reference signal;

the first signal processing circuit is configured to process the fixed-frequency reference signal to generate the plurality of fixed-frequency signals; and

a frequency of each of the plurality of fixed-frequency signals is an integer multiple of a frequency of the fixed-frequency reference signal.

21. The system of claim 20 , wherein the signal processing circuit uses a non-linear transmission line to generate the integer multiples of the frequency of the fixed-frequency reference signal.