Quantum error-correction in microwave integrated quantum circuits
In a general aspect, a quantum error-correction technique includes applying a first set of two-qubit gates to qubits in a lattice cell, and applying a second, different set of two-qubit gates to the qubits in the lattice cell. The qubits in the lattice cell include data qubits and ancilla qubits, and the ancilla qubits reside between respective nearest-neighbor pairs of the data qubits. After the first and second sets of two-qubit gates have been applied, measurement outcomes of the ancilla qubits are obtained, and the parity of the measurement outcomes is determined.
1. A quantum computing system comprising:
a quantum processor cell comprising a device lattice;
a control system communicably coupled to the quantum processor cell to control the device lattice, the control system configured to:
apply a first set of two-qubit gates to qubits in a lattice cell in the device lattice, the qubits in the lattice cell comprising data qubits and ancilla qubits, the ancilla qubits in the lattice cell residing between respective nearest-neighbor pairs of the data qubits in the lattice cell;
apply a second, different set of two-qubit gates to the qubits in the lattice cell; and
after applying the first and second sets of two-qubit gates, obtaining measurement outcomes of the ancilla qubits in the lattice cell; and
determine a parity of the measurement outcomes;
wherein the quantum processor cell includes one or more of fluxonium devices and transmon devices.
2. The quantum computing system of claim 1 , wherein applying a first set of two-qubit gates comprises applying a first set of controlled-not gates, and applying a second set of two-qubit gates comprises a second, different set of controlled-not gates.
3. The quantum computing system of claim 2 , wherein at least one of the controlled-not gates is applied to qubits defined respectively by a fluxonium device and a transmon device, and applying the controlled-not gate comprises tuning an operating frequency of the fluxonium device to an operating frequency of the transmon device.
4. The quantum computing system of claim 2 , wherein at least one of the controlled-not gates is applied to qubits defined respectively a fluxonium device and a transmon device, and applying the controlled-not gate comprises tuning an operating frequency of the fluxonium device to the |1 →|2 transition frequency of the transmon device.
5. The quantum computing system of claim 1 , wherein the lattice cell comprises:
transmon devices that define the data qubits; and
fluxonium devices that define the ancilla qubits.
6. The quantum computing system of claim 1 , wherein the lattice cell comprises:
fluxonium devices that define the data qubits; and
transmon devices that define the ancilla qubits.
7. The quantum computing system of claim 1 , wherein the lattice cell comprises:
a first group of fluxonium devices that define the data qubits; and
a second group of fluxonium devices that define the ancilla qubits.
8. The quantum computing system of claim 1 , wherein the lattice cell comprises:
a first group of transmon devices that define the data qubits; and
a second group of transmon devices that define the ancilla qubits.
9. A quantum computing system comprising:
a quantum processor cell comprising a device lattice;
a control system communicably coupled to the quantum processor cell to control the device lattice, the control system configured to:
apply a first set of two-qubit gates to qubits in a lattice cell in the device lattice, the qubits in the lattice cell comprising data qubits and ancilla qubits, the ancilla qubits in the lattice cell residing between respective nearest-neighbor pairs of the data qubits in the lattice cell;
apply a second, different set of two-qubit gates to the qubits in the lattice cell; and
after applying the first and second sets of two-qubit gates, obtaining measurement outcomes of the ancilla qubits in the lattice cell; and
determine a parity of the measurement outcomes;
wherein a rectilinear lattice comprises the lattice cell.
10. The quantum computing system of claim 9 , wherein the parity is used for quantum error-correction in a surface code applied to the rectilinear lattice.
11. The quantum computing system of claim 9 , wherein the parity is used for quantum error-correction in a color code applied to the rectilinear lattice.