Instrumentation for quantum computers

Abstract

Quantum computation poses challenging engineering and basic physics issues for the control of nanoscale systems. In particular, experimental realizations of up to seven-qubit NMR quantum computers have acutely illustrated how quantum circuits require extremely precise control instrumentation for pulsed excitation. In this thesis, we develop two general-purpose, low-cost pulse programmers and two Class E power amplifiers, designed for precise control of qubits and complex pulse excitation. The first-generation pulse programmer has timing resolutions of 235 ns, while the second-generation one has resolutions of 10 ns. The Class E power amplifier has [mu]s transient response times, a high quality-factor, and a small form factor. The verification of the pulse programmer and the Class E power amplifier is demonstrated using a customized nuclear quadrupole resonance (NQR) spectrom- eter, which incorporates both devices. The two devices control the generation of RF pulses used in NQR experiments on paradichlorobenzene (C₆H₄C₁₂) and sodium nitrite (NaNO₂). The NQR signals originating from ¹⁴N in sodium nitrite and from ³⁵Cl in paradichlorobenzene are measured using the NQR spectrometer. The pulse programmer and the Class E power amplifier represent first steps towards development of practical NMR quantum computers.