Emulator readout module

[sorewachigauyo]

As discussed in #941, to enable the emulation of the readout pulse.

This relies on knowing the bare resonator frequency, SNR of the syst-em, ADC sampling rate, Q factors of the resonator (which can be acquired from qiboteam/qibocal#917), qubit-resonator coupling, qubit frequency and anharmonicity. Though, the Q factors are power dependent, so these would only hold true for the calibrated readout amplitude.

Here is some sample code using this module to measure the transmission of the readout resonator for the ground and excited states across different readout frequencies.

import numpy as np
import matplotlib.pyplot as plt
from qibolab.qubits import Qubit
from qibolab.instruments.emulator.readout import ReadoutSimulator

bare_resonator_frequency = 5.045e9

qb = Qubit(0, bare_resonator_frequency=bare_resonator_frequency, drive_frequency=3.99e9, anharmonicity=-191.78e6)
readout = ReadoutSimulator(qubit=qb, g=30e6, noise_model=None, internal_Q=2.5e6, coupling_Q=6e4, sampling_rate=1966.08e6)

span = 1e6
center_frequency = bare_resonator_frequency + 0.75e6
freq_sweep = np.linspace(center_frequency - span / 2, center_frequency + span / 2, 1000)
y_gnd = np.abs(readout.ground_s21(freq_sweep))
y_exc = np.abs(readout.excited_s21(freq_sweep))

freq_sweep /= 1e9
plt.plot(freq_sweep, y_gnd, label=r"$|0\rangle$")
plt.plot(freq_sweep, y_exc, label=r"$|1\rangle$")
plt.ylabel("|S21| [arb. units]")
plt.xlabel("Readout Frequency [GHz]")
plt.legend()
plt.grid()
plt.tight_layout()
plt.savefig("S21.png", dpi=300)
plt.show()

Here is some sample code of using the readout module to emulate single shot readout for 100 shots.

import numpy as np
import matplotlib.pyplot as plt
from qibolab.qubits import Qubit
from qibolab.instruments.emulator.readout import ReadoutSimulator
from qibolab.pulses import ReadoutPulse

bare_resonator_frequency = 5.045e9
nshots = 100

SNR = 50 # dB
READOUT_AMPLITUDE = 1
NOISE_AMP = np.power(10, -SNR / 20)
AWGN = lambda t: np.random.normal(loc=0, scale=NOISE_AMP, size=len(t))

qb = Qubit(0, bare_resonator_frequency=bare_resonator_frequency, drive_frequency=3.99e9, anharmonicity=-191.78e6)
readout = ReadoutSimulator(qubit=qb, g=10e6, noise_model=AWGN, internal_Q=2.5e6, coupling_Q=6e4, sampling_rate=1966.08e6)
ro_pulse = ReadoutPulse(start=0, duration=1000, amplitude=READOUT_AMPLITUDE, frequency=5.04585e9, shape="Rectangular()", relative_phase=0)

rgnd = [readout.simulate_ground_state_iq(ro_pulse) for k in range(nshots)]
rexc = [readout.simulate_excited_state_iq(ro_pulse) for k in range(nshots)]
plt.scatter(np.real(rgnd), np.imag(rgnd), label=r"$|0\rangle$")
plt.scatter(np.real(rexc), np.imag(rexc), label=r"$|1\rangle$")
plt.xlabel("I")
plt.ylabel("Q")
plt.legend()
plt.tight_layout()
plt.savefig("IQ.png", dpi=300)
plt.show()

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.
• Connect the results emulator to this readout module
• Add the relevant parameters needed to the Qubit object
• Add tests
• Use readout IF frequency instead of exact frequency for systems with mixers

@alecandido Just to confirm that this is what you mean by readout emulation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.32%. Comparing base (c566eac) to head (cbd462a).

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  Coverage   70.32%   70.32%           
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  Files          64       64           
  Lines        6679     6679           
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