Weakly tunable qubit based on two coupled disparate transmons
A technique relates to providing a superconducting quantum device. A fixed frequency transmon qubit is provided. A tunable frequency transmon qubit is provided. The fixed frequency transmon qubit is coupled to the tunable frequency transmon qubit to form a single qubit.
1. A method of providing a superconducting quantum device, the method comprising:
providing a fixed frequency transmon qubit;
providing a tunable frequency transmon qubit consisting of only a first Josephson junction, a second Josephson junction, and a capacitor, both the first and second Josephson junctions being in parallel to the capacitor; and
coupling the fixed frequency transmon qubit to the tunable frequency transmon qubit by a direct connection to form a single qubit.
2. The method of claim 1 , wherein the fixed frequency transmon qubit shares a node with the tunable frequency transmon qubit as the direct connection; and
wherein both the fixed frequency transmon qubit and the tunable frequency transmon qubit are capacitively coupled via a coupling capacitor to form another connection.
3. The method of claim 1 , wherein the fixed frequency transmon qubit is shunted by a first capacitor.
4. The method of claim 3 , wherein the tunable frequency transmon qubit is shunted by the capacitor, a value of the first capacitor being greater than the capacitor.
5. The method of claim 1 , wherein the tunable frequency transmon qubit is a direct current superconducting quantum interference device (dc-SQUID).
6. The method of claim 5 , wherein the dc-SQUID is asymmetric.
7. The method of claim 5 , wherein the dc-SQUID includes two Josephson junctions (JJs), the two JJs being the first JJ and the second JJ.
8. The method of claim 7 , wherein the first JJ is larger than the second JJ.
9. The method of claim 1 , wherein a qubit resonance frequency of the single qubit is defined by both the fixed frequency transmon qubit and the tunable frequency transmon qubit.
10. The method of claim 9 , wherein a shift in the qubit resonance frequency of the single qubit is induced by a frequency shift in the tunable frequency transmon qubit.
11. A superconducting quantum device comprising:
a fixed frequency transmon qubit; and
a tunable frequency transmon qubit consisting of only a first Josephson junction, a second Josephson junction, and a capacitor, both the first and second Josephson junctions being in parallel to the capacitor, the fixed frequency transmon qubit being coupled to the tunable frequency transmon qubit by a direct connection in order to form a single qubit.
12. The quantum device of claim 11 , wherein the fixed frequency transmon qubit and the tunable frequency transmon qubit share one node and are capacitively coupled via a coupling capacitor.
13. The quantum device of claim 11 , wherein the fixed frequency transmon qubit is shunted by a first capacitor.
14. The quantum device of claim 13 , wherein the tunable frequency transmon qubit is shunted by the capacitor, a value of the first capacitor being greater than the capacitor.
15. The quantum device of claim 11 , wherein the tunable frequency transmon qubit is a direct current superconducting quantum interference device (dc-SQUID).
16. The quantum device of claim 15 , wherein the dc-SQUID is asymmetric.
17. The quantum device of claim 15 , wherein the dc-SQUID includes two Josephson junctions (JJs), the two JJs being the first JJ and the second JJ.
18. The quantum device of claim 17 , wherein the first JJ is larger than the second JJ.
19. A method of configuring a single qubit, the method comprising:
providing a single Josephson junction (JJ) shunted by a first capacitor which together form a fixed frequency transmon qubit;
providing an asymmetric direct current superconducting quantum interference device (dc-SQUID) shunted by a second capacitor which together from a tunable frequency transom qubit; and
connecting the single JJ to the dc-SQUID by a direct connection through one shared node;
defining a qubit resonance frequency of the single qubit by both the fixed frequency transmon qubit and the tunable frequency transmon qubit.
20. The method of claim 19 , wherein both the single JJ and the asymmetric dc-SQUID sharing the one shared node are capacitively coupled together via a coupling capacitor.
21. The method of claim 19 , wherein a value of the first capacitor is greater than the second capacitor.
22. The method of claim 19 , wherein the qubit resonance frequency of the single qubit is configured to be shifted.
23. The method of claim 22 , wherein a shift in the qubit resonance frequency of the single qubit is induced by the asymmetric dc-SQUID.
24. A single qubit comprising:
a single Josephson junction (JJ) transmon qubit shunted by a first capacitor which together from a tunable frequency transmon qubit; and
an asymmetric direct current superconducting quantum interference device (dc-SQUID), the asymmetric dc-SQUID being shunted by a second capacitor which together form a tunable frequency transmon qubit;
wherein a state of the single qubit is based on a combination of the single JJ transmon qubit coupled to the asymmetric dc-SQUID;
wherein a qubit resonance frequency of the single qubit is defined by both the fixed frequency transmon qubit and the tunable frequency transmon qubit.
25. A method of providing an energy system of a single qubit, the method comprising:
providing the single qubit configured as a fixed frequency transmon qubit coupled by a direct connection to a tunable frequency transmon qubit, wherein a qubit resonance frequency of the single qubit is defined by both the fixed frequency transmon qubit and the tunable frequency transmon qubit; and
generating the energy system of the single qubit as a V energy system such that readout of the single qubit is configured to be performed by coupling to a 4 th energy level or a 7 th energy level of the single qubit.