The Phase Gate

The programmable phase gate P(theta) writes a tunable phase onto a qubit - the mechanism Kronos uses to encode a material's energies for read-out.

What it does

P(theta) = [[1,0],[0,e^(i*theta)]] leaves |0> alone and rotates |1> by theta. S and T are the special cases theta = pi/2 and pi/4.

Where it appears at Kronos

Precisely tuned phase gates are the core of the quantum Fourier transform and phase estimation - the routine that turns a material Hamiltonian's eigenvalues into a number Kronos can measure.

Honest note

High-precision phase estimation on real molecules waits on error correction, ~mid-2030s.