39 research outputs found
Active inductor shunt peaking in high-speed VCSEL driver design
An all transistor active inductor shunt peaking structure has been used in a
prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical
link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated
in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation
tolerant purpose. The all transistor active inductor shunt peaking is used to
overcome the bandwidth limitation from the CMOS process. The peaking structure
has the same peaking effect as the passive one, but takes a small area, does
not need linear resistors and can overcome the process variation by adjust the
peaking strength via an external control. The design has been tapped out, and
the prototype has been proofed by the preliminary electrical test results and
bit error ratio test results. The driver achieves 8-Gbps data rate as simulated
with the peaking. We present the all transistor active inductor shunt peaking
structure, simulation and test results in this paper.Comment: 4 pages, 6 figures and 1 table, Submitted to 'Chinese Physics C
Demonstration of Adiabatic Variational Quantum Computing with a Superconducting Quantum Coprocessor
Adiabatic quantum computing enables the preparation of many-body ground
states. This is key for applications in chemistry, materials science, and
beyond. Realisation poses major experimental challenges: Direct analog
implementation requires complex Hamiltonian engineering, while the digitised
version needs deep quantum gate circuits. To bypass these obstacles, we suggest
an adiabatic variational hybrid algorithm, which employs short quantum circuits
and provides a systematic quantum adiabatic optimisation of the circuit
parameters. The quantum adiabatic theorem promises not only the ground state
but also that the excited eigenstates can be found. We report the first
experimental demonstration that many-body eigenstates can be efficiently
prepared by an adiabatic variational algorithm assisted with a multi-qubit
superconducting coprocessor. We track the real-time evolution of the ground and
exited states of transverse-field Ising spins with a fidelity up that can reach
about 99%.Comment: 12 pages, 4 figure
Experimental Simulation of Larger Quantum Circuits with Fewer Superconducting Qubits
Although near-term quantum computing devices are still limited by the
quantity and quality of qubits in the so-called NISQ era, quantum computational
advantage has been experimentally demonstrated. Moreover, hybrid architectures
of quantum and classical computing have become the main paradigm for exhibiting
NISQ applications, where low-depth quantum circuits are repeatedly applied. In
order to further scale up the problem size solvable by the NISQ devices, it is
also possible to reduce the number of physical qubits by "cutting" the quantum
circuit into different pieces. In this work, we experimentally demonstrated a
circuit-cutting method for simulating quantum circuits involving many logical
qubits, using only a few physical superconducting qubits. By exploiting the
symmetry of linear-cluster states, we can estimate the effectiveness of
circuit-cutting for simulating up to 33-qubit linear-cluster states, using at
most 4 physical qubits for each subcircuit. Specifically, for the 12-qubit
linear-cluster state, we found that the experimental fidelity bound can reach
as much as 0.734, which is about 19\% higher than a direct simulation {on the
same} 12-qubit superconducting processor. Our results indicate that
circuit-cutting represents a feasible approach of simulating quantum circuits
using much fewer qubits, while achieving a much higher circuit fidelity