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Technical details about Helmi

Architecture and Topology

Helmi is a 5-qubit quantum Computer co-developed by VTT and IQM using superconducting qubits. The qubits are arranged in a star shaped topology, with the central qubit being Qubit 3 (QB3) connected to the other 4 qubits. This means that any two-qubit gate will work most efficiently between QB3 and any other qubit, whereas one-qubit gates can be mapped to any of the 4 surrounding qubits.

Helmi's node mapping

Native Gates

Helmi's native gates are the two-qubit Control-Z and a the one-qubit rotational gate around the x-y plane.

Defining topology and gates in Qiskit and Cirq

To define the features of Helmi in Qiskit and Circ, for example for transpiling, use the following definitions:

Helmi Qiskit Cirq
Basis Gates CZ + Rx, Ry, Rz basis_gates=['r', 'cz'] NATIVE_GATES=ops.PhasedXPowGate, ops.XPowGate, ops.YPowGate, ops.CZPowGate()
Connectivity Star Shaped coupling_map=[[2, 0], [2, 1], [2, 3], [2, 4]] CONNECTIVITY=({1, 3}, {2, 3}, {4, 3}, {5, 3})
Mapping virtual_qubits=circuit_decomposed.qubits
Dictionary qubit_mapping={'NamedQubit1':'QB1','NamedQubit2':'QB3'}

With Qiskit you will need to decompose your circuit with the basis gate and define your qubit mapping before running. With Cirq this is not necessary.

(Note that native gates and basis gates are interchangeable.)

Further Reading

Last update: November 2, 2022