Quickstart

A brief introduction to using QdcEm to emulate a distributed quantum gate across two virtual QPUs on a single superconducting chip. We illustrate this by constructing a two-QPU layout and applying a noisy remote CNOT gate.

• `Download the Main notebook <https://github.com/<your-org>/QdcEm/blob/main/Main.ipynb>`__, or

• read through the text below and code along.

Contents:

• 1. Imports

• 2. Define qubit registers

• 3. Apply a noisy remote CNOT

• 4. Run on the Aer simulator

1. Imports

First, import the necessary Qiskit and QdcEm components:

from qiskit.circuit import QuantumCircuit, QuantumRegister, ClassicalRegister
from QdcEm.QPU import Make, Get_Initial_Layout
from QdcEm.RemoteGates import remote_cx

2. Define qubit registers

Create a five-qubit register and assign roles. Each QPU requires one communication qubit, one environment qubit, and one or more processing qubits.

qreg = QuantumRegister(5, 'q')
creg = ClassicalRegister(4, 'c')
qc   = QuantumCircuit(qreg, creg)

# QPU A: processing on q[2], communication on q[0], environment on q[1]
qpu_A = Make(Comm=qreg[0], EN=qreg[1], Processing_Qubits=[qreg[2]])

# QPU B: communication on q[3], environment on q[4]
qpu_B = Make(Comm=qreg[3], EN=qreg[4], Processing_Qubits=[])

3. Apply a noisy remote CNOT

The remote_cx function appends the full Cat-Comm protocol — Bell pair generation, CM noise injection, mid-circuit measurements, and feed-forward corrections — directly to the circuit.

remote_cx(
    qc,
    control           = qreg[2],   # processing qubit in QPU A
    target            = qreg[3],   # processing qubit in QPU B
    CommA             = qpu_A.Comm,
    CommB             = qpu_B.Comm,
    ENA               = qpu_A.EN,
    ENB               = qpu_B.EN,
    creg              = creg,
    creg_index        = 0,
    kappa_Fiber       = 0.05,      # sqrt(0.01 * alpha), one 10 m segment
    Steps             = 3,         # three additional 10 m fiber collisions
    kappa_Transductor = 0.1,
)

qc.measure(qreg[2], creg[2])
qc.measure(qreg[3], creg[3])

4. Run on the Aer simulator

from qiskit_aer import AerSimulator

simulator = AerSimulator()
job = simulator.run(qc, shots=1024)
result = job.result()
counts = result.get_counts()
print(counts)

Note

To run on real IBM hardware, replace AerSimulator() with a backend obtained via QiskitRuntimeService and pass the initial_layout produced by Get_Initial_Layout at transpile time.