Quantum computing structures and resonators thereof

1. A resonator for use in quantum computing, the resonator comprising:

a housing disposed along a resonator axis, the housing having a first portion extending from a housing distal end to near a qubit location and a second portion extending from near the qubit location to a housing proximal end,

the housing defining a cavity extending from a cavity proximal end to a cavity distal end along a portion of the resonator axis,

wherein the housing comprises a protrusion extending axially from the housing distal end along the resonator axis to near the qubit location, a proximal portion of the protrusion comprising a tapered portion; and

a qubit extending into the cavity at the qubit location.

2. The resonator of claim 1 , wherein an inner diameter of the cavity at the cavity distal end is greater than an inner diameter of the cavity at the cavity proximal end, each inner diameter measured from opposing sidewalls of the housing.

3. The resonator of claim 1 , wherein at least a portion of the first portion of the housing comprises niobium.

4. The resonator of claim 1 , wherein at least a portion of the second portion of the housing comprises aluminum, copper, or both.

5. The resonator of claim 1 , comprising a Josephson junction disposed on or near the qubit.

6. The resonator of claim 5 , wherein the qubit comprises a transmon.

7. The resonator of claim 1 , wherein the protrusion comprises an axially tapering diameter at the proximal portion.

8. The resonator of claim 1 , wherein the first portion of the housing comprises a tapered portion.

9. The resonator of claim 1 , wherein a shape of the protrusion is generally cylindrical.

10. The resonator of claim 1 , wherein a distance between the protrusion and a housing sidewall within the cavity is at a minimum at the proximal portion of the protrusion.

11. The resonator of claim 1 , wherein a shape of a proximal portion of the cavity is generally cylindrical.

12. The resonator of claim 1 , wherein the housing comprises an aperture configured to allow evacuation of the cavity therethrough.

13. The resonator of claim 1 , further comprising a seam between the first and second portions of the housing.

14. The resonator of claim 13 , wherein the aperture is disposed within the proximal portion of the housing.

15. The resonator of claim 1 , further comprising a second qubit within the resonator, the second qubit being in electrical communication with the qubit.

16. The resonator of claim 1 , further comprising a second protrusion extending axially from the housing proximal end along the resonator axis.

17. The resonator of claim 1 , wherein the housing forms an axial gap disposed radially outward of a main chamber of the housing.

18. A method of manufacturing a quantum computing resonator, the method comprising:

forming a cavity generally along a longitudinal axis within a housing extending axially from a cavity proximal end to a cavity distal end, the housing having a proximal portion and a distal portion;

forming a protrusion within the housing, the protrusion extending axially from the distal portion of the housing through a portion of the cavity, a proximal portion of the protrusion having a tapered diameter; and

disposing a qubit within the resonator.

19. The method of claim 18 , wherein disposing the qubit within the resonator comprises disposing the qubit near the proximal portion of the protrusion.

20. The method of claim 18 , wherein forming the cavity generally along the longitudinal axis within the housing comprises:

forming the proximal portion of the housing;

forming the distal portion of the housing; and

bonding the proximal and distal portions of the housing together generally along the longitudinal axis.