Pulse Player
Hear Quantum Gate Pulses
Superconducting qubits are controlled by shaped microwave pulses at ~5 GHz. Each pulse is tuned to its qubit’s resonant frequency — the same way a radio picks up only its station. Press play to hear them.
Simplest entangling circuit: Ry(π/2) → CZ → Ry(π/2). Creates |00⟩+|11⟩.
Pitch shift is physically accurate
What You’re Hearing
Each gate type produces a different pulse shape. Here’s the legend.
DRAG pulse (Motzoi 2009): lifted Gaussian I-channel, β×derivative Q-channel. Suppresses leakage to |2⟩.
π-rotation DRAG. Same shape as Ry, scaled to a full flip.
Sudden Net-Zero flux (Negirneac 2021): two rectangular lobes of opposite polarity. Leakage destructively interferes.
Virtual Z-gate (McKay 2017): phase update in software. Zero duration, zero error, no physical pulse.
GaussianSquare readout: flat-top pulse at the resonator frequency with Gaussian rise/fall ramps.
Why It Sounds Like This
The physics behind the frequencies, shapes, and timing.
Resonance
These pulses work because the microwave frequency matches the qubit’s energy gap: E = h×f. A 5 GHz qubit absorbs 5 GHz photons. Off-resonance, the pulse bounces off. This is why each qubit sounds like a different pitch — they’re fabricated at different frequencies so pulses don’t crosstalk.
Explore resonance →Parallel Scheduling
Gates on independent qubits execute simultaneously, just like real hardware. CZ gates block both qubits; single-qubit gates only block one. This 2-qubit circuit takes 740 ns — shorter than sequential because parallel gates overlap. The schedule above shows exactly when each pulse fires.
Why DRAG Pulses Are Shaped This Way
A transmon isn’t a perfect two-level system — it has a third level |2⟩ nearby. A plain Gaussian would leak population there. DRAG adds a derivative correction on the Q-channel (β×dG/dt) that cancels this leakage. The 4σ truncation and lifted baseline ensure the pulse starts and ends at exactly zero.
Why CZ Pulses Have Two Lobes
The Sudden Net-Zero CZ (Negirneac 2021) intentionally maximizes leakage in each lobe — then the two opposite-polarity lobes destructively interfere, canceling the leakage while accumulating a conditional π-phase. The net-zero constraint (∫Φdt = 0) also cancels low-frequency flux noise.
References
Motzoi et al., “Simple pulses for elimination of leakage in weakly nonlinear qubits,” PRL 103, 110501 (2009)
Gambetta et al., “Analytic control methods for high-fidelity unitary operations,” PRA 83, 012308 (2011)
McKay et al., “Efficient Z gates for quantum computing,” PRA 96, 022330 (2017)
Rol et al., “Fast, high-fidelity conditional-phase gate exploiting leakage interference,” PRL 123, 120502 (2019)
Negirneac et al., “High-fidelity controlled-Z gate with maximal intermediate leakage,” PRL 126, 220502 (2021)