VTT Q5 "Helmi"
VTT Q5 is a 5 qubit superconducting quantum computer computer co-developed and built by IQM and VTT. It uses flux-tunable qubits and couplers which are described in this paper1.
Helmi's qubits are arranged in a star-shaped topology, meaning that the central qubit, QB3, is connected to all of the outer qubits, QB1, QB2, QB4. Two-qubit gates can be applied only between the central qubit and the outer qubits.
The qubits are pairwise connected with tunable couplers.
Native-gate set
To run arbitrary quantum circuits, a QPU needs to implement a universal gate set. Helmi implements the following gates natively:
- Single-qubit gates: Phased-\(RX\) gate (PRX)
- Two-qubit gate: Controlled-\(Z\) gate (CZ)
Measurements are natively implemented as single-qubit measurements in the \(Z\) basis.
Characteristics
The values below are averaged values. Actual values might differ from day-to-day.
| QB1 | QB2 | QB3 | QB4 | QB5 | |
|---|---|---|---|---|---|
| Drive Frequencies [GHz] | 4.4 | 3.9 | 4.2 | 4.4 | 4.4 |
| Readout Frequencies [GHz] | 5.3 | 5.0 | 6.2 | 5.9 | 5.6 |
| T1 time [µs] | 35.5 | 25.7 | 40.2 | 41.3 | 36.0 |
| T2 time [µs] | 19.2 | 17.7 | 9.12 | 19.1 | 22.2 |
| T2 echo time [µs] | 45.2 | 33.1 | 26.5 | 47.7 | 35.0 |
| Single-Qubit Gate Fidelities2 [%] | 99.4 | 99.7 | 99.7 | 99.6 | 99.7 |
| Readout Fidelities [%] | 96 | 95 | 95 | 95 | 95 |
The coupler characteristics are given below. TC refers to tunable coupler.
| TC-3-1 | TC-3-2 | TC-3-4 | TC-3-5 | |
|---|---|---|---|---|
| Two-qubit Gate Fidelities3 [%] | 96.4 | 95.9 | 94.6 | 97.5 |
The PRX gate length and the CZ gate length is 120 [ns] respectively.
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Long-Distance Transmon Coupler with cz-Gate Fidelity above 99.8%, Marxer et al. ↩
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Calculated via randomized benchmarking ↩
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CZ gate fidelity calculated via interleaved randomized benchmarking ↩