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The Qwerty Quantum Programming Language #

Qwerty is a new basis-oriented quantum programming language. Instead of writing quantum gates, Qwerty programs are expressed with higher-level primitives (namely the basis translation) or with classical logic.

Compare one iteration of Grover’s algorithm in Qwerty versus Q#:

  • Qwerty 
    @classical
def oracle(x: bit[4]) -> bit:
    return x[0] & ~x[1] & x[2] & ~x[3]

@qpu[[N]]
def grover_iter(q):
    return (q | oracle.sign
              | 'p'**N >> -'p'**N)
  • Q# (based on an official Q# example) 
    operation GroverIter(q: Qubit[]) : Unit {
    use ancilla = Qubit();
    within {
        X(ancilla);
        H(ancilla);
        X(q[1]);
        X(q[3]);
    } apply {
        Controlled X(q, ancilla);
    }

    within {
        for qi in q {
            H(qi);
            X(qi);
        }
    } apply {
        Controlled Z(Most(q), Tail(q));
    }
}

In the Qwerty code above, (1) the oracle is defined using classical logic; (2) the compiler synthesizes the phase kickback trick automatically from oracle.sign; and (3) the diffusion step is achieved with the basis translation 'p'**N >> -'p'**N instead of handwritten circuitry.

Qwerty is embedded in Python, so invoking a Qwerty program is as easy as python grover.py.

For more information, see: