pong.qasm

/*
 * 0 |   CNOT   |
 * 1 |   CNOT   |
 * 2 PPPMMMMMMPPP
 */

gatecal pong(amp) q0 [duration] {
    play d0, gaussian(amp, duration)
}

gatecal pong_cx(amp) q0, q1, q2{
    barrier q0, q1, q2;
    cross-res(pi/4) 0, 1
    x(pi) 0;  // this is a gatecal
    cross-res(-pi/4) 0, 1;
    glue[1]-pong(amp) q2;
    glue[2]-pong(-amp) q2;
    glue[1]-pong(amp) q2;
    barrier q0, q1, q2;
}

barrier 0, 1, 2
glue[1]-delay(0) 0;    // these stretchable delays would be inserted by a high-level scheduling pass.
glue[1]-delay(0) 1;    // it should be possible to write regular QASM using those ponged CNOTs
glue[1]-delay(0) 2;    // even if you don't care how the whole program is aligned (left of right)
h 0;
pong-cx 0, 1, 2;
barrier 0, 1, 0


//boxto conditional, anonymous subroutine (named boxto not supported)

length maxduration = 1us

barrier q[0], q[1];
slowgate q[0];
delay[stretch] q[1];  
h q[1]; 
measure q[1] -> c[0]; 
delay[stretch] q[1];
boxto[maxduration] { // fixed-duration anonymous subroutine
    if c==0: U(0.1, 0.2, 0.3) q[1]  // duration depends on result of measurement
    delay[stretch]                  // glue to allow to stretch (can be implicit)
} // throw runtime error if `box` does not conclude by maxduration
delay[stretch] q[1];
barrier q[0], q[1];