Correlated Random Number Generation

This example demonstrates how two nodes can generate a shared random bit using quantum entanglement. Found in examples/new-sdk/corrRNG/.

The protocol

  1. Alice creates an EPR pair (two maximally entangled qubits A and B) with Bob:

\[|\Phi^{+}\rangle = = \frac{1}{\sqrt{2}} \left(|0\rangle_A |0\rangle_B + |1\rangle_A |1\rangle_B\right)\]

  1. Both Alice and Bob measure their respective qubits.

  2. Because the qubits are entangled, both measurements yield the same random bit.

Alice’s code

From aliceTest.py:

def run_alice(this_node_name: str, remote_node_name: str) -> int:
    epr_socket = EPRSocket(remote_node_name)

    # sim_conn is our connection to the quantum backend (SimulaQron), not to Bob.
    # Bob is reached via EPRSocket for quantum and reader/writer for classical.
    sim_conn = NetQASMConnection(this_node_name, epr_sockets=[epr_socket])

    # Create an entangled qubit
    A = epr_socket.create_keep()[0]

    # And simply measure it
    a = A.measure()

    # flush() executes all queued quantum operations and makes measurement
    # results available.  Before flush(), a is just a future/promise.
    sim_conn.flush()

    # int(m) extracts the measurement outcome — only valid after flush().
    a_val = int(a)
    sim_conn.close()
    return a_val

Bob’s code

From bobTest.py — the key difference is the usage of recv_keep() instead of create_keep(); the rest of the code is analogous to Alice’s:

def run_bob(this_node_name: str, remote_node_name: str) -> int:
    epr_socket = EPRSocket(remote_node_name)

    # sim_conn is our connection to the quantum backend (SimulaQron), not to Alice.
    # Alice is reached via EPRSocket for quantum and reader/writer for classical.
    sim_conn = NetQASMConnection(this_node_name, epr_sockets=[epr_socket])

    # Receive an entangled qubit
    B = epr_socket.recv_keep()[0]

    # And simply measure it
    b = B.measure()

    # flush() executes all queued quantum operations and makes measurement
    # results available.  Before flush(), b is just a future/promise.
    sim_conn.flush()

    # int(m) extracts the measurement outcome — only valid after flush().
    b_val = int(b)
    sim_conn.close()
    return b_val

Key concepts

  • EPRSocket handles entanglement between nodes. One side calls create_keep(), the other calls recv_keep().

  • sim_conn is the connection to the quantum backend, not to the other node.

  • Both nodes get the same random bit because measuring one half of an EPR pair determines the outcome of the other.

Running

cd examples/new-sdk/corrRNG
bash run.sh

Expected output (the bit value is random):

Alice: My Random Number is 'X'
Bob: My Random Number is 'X'

where \(x\in{0,1}\).