A valid question to ask is, how many randomly compiled circuits do we need to see a benefit from randomized compiling (RC)? We re-analyzed the random circuit sampling data presented on the RC project page to answer this question. For each circuit depth (K) in which we generated random circuits, we computed the convergence of
We performed state tomography on a single-qubit at three different points during a random sequence of gates (after 10 gates, after 100 gates, and after 200 gates). This clearly demonstrates the intuition behind randomized compiling (RC): coherent errors can build up as a function of circuit depth, resulting in errors in the bare quantum state
One significant source of error in CR gates, especially when minimizing gate time, is leakage of the quantum state out of the computational subspace, in particular to the second excited state of the control transmon. We have observed and characterized this leakage channel during the CR gate by monitoring directly the second excited states of
To measure the dynamics of the CR gate, we perform Hamiltonian tomography. This experiment involves driving the CR interaction and performing state tomography on the target qubit, thus allowing one to measure the Bloch dynamics of the target qubit, conditioned on the control qubit state. We run this experiment when with the control qubit in
Randomized Benchmarking (RB) is a standard experiment to quantify the error rate of a quantum gate set. In addition to being relevant for building fault-tolerant quantum computers, reducing two-qubit gate error rates enables the execution of NISQ algorithms with larger-depth. However, environmental drift is a ubiquitous phenomenon in quantum hardware, and it is important to
Crosstalk remains a major issue in the design of microwave drive lines for fast single qubit control. Microwave drive lines for qubit control must be placed sufficiently far from the qubit to limit the qubit-drive line coupling and the resulting decrease in qubit lifetimes via the purcell effect. However, this generally leads to an increase
Simulations of two qubit gate dynamics have illustrated the well known trade-off between coherent and incoherent errors as a function of gate speed. Faster gates are less susceptible to the incoherent error caused by qubit relaxation, while slower gates have lower levels of coherent error due to unwanted interactions with the non-computational states of the
First acquisition of long trajectories (~ms) to test detector performance when the photon’s arrival time is unknown. The blue trace is the filtered detector response when a weak continuous tone was sent into the detector. Same for the orange trace, except the tone was off so when the trajectory crosses the threshold we measure a
Junction fabrication process is ported to a new oxygen plasma asher. This new tool significantly simplifies the process, improves critical current uniformity, and improves the uniformity of how the junctions age with time.