cunqa.qc_protocols

Quantum-communication protocols for distributed circuits.

This subpackage provides the high-level helpers built on top of the gen_ent primitive to communicate quantum information between circuits running on different vQPUs:

  • Teledata (qsend / qrecv): teleports the state of a data qubit from one circuit to another.

  • Telegate (cat_entangler / cat_disentangler): shares a control qubit across circuits so that remote controlled gates can be applied locally.

These functions reserve communication qubits on the participating circuits (created via the CunqaCircuit((num_data, num_comm), num_clbits) form), so each circuit must declare enough comm qubits beforehand.

qsend(circuit, data_qubit, comm_qubit, clbits, recving_circuit, tag=None)

Teledata sender: teleports the state of data_qubit from circuit to a remote circuit.

This is the teleportation-protocol counterpart of qrecv, which must be applied on the receiving circuit with the same tag. Internally it generates the shared entanglement with gen_ent, performs the Bell measurement and sends the two classical correction bits to the remote circuit.

Parameters:

  • circuit (CunqaCircuit) – circuit holding the qubit to be teleported.

  • data_qubit (int) – computation qubit whose state is teleported.

  • comm_qubit (int) – communication qubit employed to send.

  • clbits (list[int]) – two classical bits used to store the Bell-measurement outcomes.

  • recving_circuit (str | CunqaCircuit) – id of the circuit or circuit object to which the qubit is teleported.

  • tag (str) – identifier shared with the matching qrecv call.

Return type:

None

qrecv(circuit, data_qubit, comm_qubit, clbits, control_circuit, tag=None)

Teledata receiver: reconstructs into data_qubit the state teleported by a remote circuit.

This is the receiving counterpart of qsend and must be called with the same tag. Internally it generates the shared entanglement with gen_ent, receives the two classical correction bits and applies the conditional Pauli corrections.

Parameters:

  • circuit (CunqaCircuit) – circuit that receives the teleported state.

  • data_qubit (int) – computation qubit to which the received state is assigned.

  • comm_qubit (int) – communication qubit employed to receive.

  • clbits (list[int]) – two classical bits used to store the received correction bits.

  • control_circuit (str | CunqaCircuit) – id of the circuit or circuit object from which the qubit is received.

  • tag (str) – identifier shared with the matching qsend call.

Return type:

None

cat_entangler(target_circuits, data_qubit, comm_qubits, clbits, tag=None)

Telegate entangler: distributes the control state of data_qubit (held by the first circuit in target_circuits) onto the comm qubits of the remaining circuits, so that they can apply gates locally controlled by it.

It opens a telegate block that must be closed with cat_disentangler using the same set of target_circuits. Between the two calls, each receiving circuit applies the gate(s) controlled on its comm qubit. Internally it requests the shared GHZ state with gen_ent.

Parameters:

  • target_circuits (list[CunqaCircuit]) – participating circuits; the first one owns the control data_qubit and the rest receive it on their comm qubit.

  • data_qubit (int) – control qubit (in the first circuit) to be shared.

  • comm_qubits (list[int]) – comm qubit of each circuit in target_circuits.

  • clbits (list[int]) – classical bit used by each circuit for the entangler corrections.

  • tag (str) – identifier shared with the matching cat_disentangler call.

cat_disentangler(target_circuits, data_qubit, comm_qubits, recv_clbits, send_clbits)

Telegate disentangler: closes the telegate block opened by cat_entangler, undoing the shared entanglement and restoring the comm qubits, while propagating the required phase correction back to the control data_qubit.

It must be called with the same target_circuits used in the matching cat_entangler, after the receiving circuits have applied their controlled gates.

Parameters:

  • target_circuits (list[CunqaCircuit] | list[str]) – the same participants passed to cat_entangler; the first one owns the control data_qubit.

  • data_qubit (int) – control qubit (in the first circuit) the correction is applied to.

  • comm_qubits (list[int]) – comm qubit of each receiving circuit.

  • recv_clbits (list[int]) – classical bits the first circuit uses to receive the corrections.

  • send_clbits (list[int]) – classical bits the receiving circuits use to send their corrections.