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How We Tune a Qubit

Calibration starts with spectroscopy: sweep frequency, find the response peak, and tune the microwave drive until the qubit is controllable. These interactives make the hidden assumptions visible: steady-state vs pulsed measurements, and why stronger drive both helps and hurts.

CW vs Pulsed Spectroscopy

CW = steady-statePulse = finite-time
Focus
Pulse Length350 ns
-50-2502550P(|1>)Detuning (MHz)
CW steady-state Lorentzianpi-pulse sinc^2 spectrumLonger pulses narrow the main lobe but create side lobes.

Saturation & Power Broadening

Two-level CW modelgamma = 1 MHz
Drive Amplitude Omega1.20 MHz
Peak: 0.30FWHM: 1.56 MHz
-12-60612P(|1>)Detuning (MHz)

Stronger drive raises the signal but saturates at 0.5 in CW steady-state, while the linewidth grows as sqrt(1+s). That tradeoff is why calibration uses both weak and strong drives, depending on what you are measuring.

Series Map

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How We Tune a Qubit

Spectroscopy + calibration basics.

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Why Qubits Forget

T1, T2, decoherence, and linewidth.

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How Qubits Talk

Avoided crossings and coupling.

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How Gates Happen

Pulses, leakage, and control errors.

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How We Measure

Dispersive readout + fidelity.

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How We Scale

Topology, routing, and spectral crowding.

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