Skip to main content
← zooHow Qubits WorkWhy Qubits Forget

Why Qubits Forget

A qubit can lose energy (T1) and lose phase coherence (T2). These times set how long quantum information survives and how sharp the resonance peak becomes. Use the controls to see how relaxation and dephasing change the signal.

Energy Relaxation vs Dephasing

Exponential decaySingle qubit
T135 us
T222 us
Ideal limit: T2 <= 2 * T1 (70 us)
03570105Remaining signalTime (us)
Energy relaxation (T1)Phase coherence (T2)Dephasing usually happens faster than energy loss.

Linewidth and Q

Homogeneous broadeningLorentzian
T220 us
f05.00 GHz
FWHM: 15.9 kHzQ: 314K
-30-1501530P(|1>)Detuning (MHz)

Linewidth is set by T2: FWHM = 1 / (pi * T2). Q is not an independent knob; it is fixed by f0 and linewidth.

Series Map

Live

How We Tune a Qubit

Spectroscopy + calibration basics.

Open →
Live

Why Qubits Forget

T1, T2, decoherence, and linewidth.

Open →
Live

How Qubits Talk

Avoided crossings and coupling.

Open →
Live

How Gates Happen

Pulses, leakage, and control errors.

Open →
Live

How We Measure

Dispersive readout + fidelity.

Open →
Live

How We Scale

Topology, routing, and spectral crowding.

Open →