ICARUS-Q: A scalable RFSoC-based control system for superconducting quantum computers

  1. Kun Hee Park,
  2. Yung Szen Yap,
  3. Yuanzheng Paul Tan,
  4. Christoph Hufnagel,
  5. Long Hoang Nguyen,
  6. Karn Hwa Lau,
  7. Stavros Efthymiou,
  8. Stefano Carrazza,
  9. Rangga P. Budoyo,
  10. and Rainer Dumke
We present a control and measurement setup for superconducting qubits based on Xilinx 16-channel radio frequency system on chip (RFSoC) device. The proposed setup consists of four parts:
multiple RFSoC FPGA boards, a setup to synchronise every DAC and ADC channel across multiple boards, a low-noise DC current supply for qubit biasing and cloud access for remotely performing experiments. We also design the setup to be free of physical mixers. The FPGA boards directly generate microwave pulses using sixteen DAC channels up to the third Nyquist zone which are directly sampled by its eight ADC channels between the fifth and the ninth zones.

Ghost Factors in Gauss Sum Factorization with Transmon Qubits

  1. Lin Htoo Zaw,
  2. Yuanzheng Paul Tan,
  3. Long Hoang Nguyen,
  4. Rangga P. Budoyo,
  5. Kun Hee Park,
  6. Zhi Yang Koh,
  7. Alessandro Landra,
  8. Christoph Hufnagel,
  9. Yung Szen Yap,
  10. Teck Seng Koh,
  11. and Rainer Dumke
A challenge in the Gauss sums factorization scheme is the presence of ghost factors – non-factors that behave similarly to actual factors of an integer – which might lead
to the misidentification of non-factors as factors or vice versa, especially in the presence of noise. We investigate Type II ghost factors, which are the class of ghost factors that cannot be suppressed with techniques previously laid out in the literature. The presence of Type II ghost factors and the coherence time of the qubit set an upper limit for the total experiment time, and hence the largest factorizable number with this scheme. Discernability is a figure of merit introduced to characterize this behavior. We introduce preprocessing as a strategy to increase the discernability of a system, and demonstrate the technique with a transmon qubit. This can bring the total experiment time of the system closer to its decoherence limit, and increase the largest factorizable number.

An experimental platform for hybridization of atomic and superconducting quantum systems

  1. Alessandro Landra,
  2. Christoph Hufnagel,
  3. Lim Chin Chean,
  4. Thomas Weigner,
  5. Yung Szen Yap,
  6. Long Hoang Nguyen,
  7. and Rainer Dumke
Hybrid quantum systems have the potential of mitigating current challenges in developing a scalable quantum computer. Of particular interest is the hybridization between atomic and
superconducting qubits. We demonstrate a novel experimental setup for transferring and trapping ultracold atoms inside a millikelvin cryogenic environment, where interactions between atomic and superconducting qubits can be established, paving the way for hybrid quantum systems. 87Rb atoms are prepared in a conventional magneto-optical trap and transported via a magnetic conveyor belt into a UHV compatible dilution refrigerator with optical access. We store 5×108 atoms with a lifetime of 794 seconds in the vicinity of the millikelvin stage.

Charge-Qubit-Resonator-Interface-Based Nonlinear Circuit QED

  1. Deshui Yu,
  2. Leong Chuan Kwek,
  3. Luigi Amico,
  4. and Rainer Dumke
We explore applications of nonlinear circuit QED with a charge qubit inductively coupled to a microwave LC resonator in the photonic engineering and ultrastrong-coupling multiphoton
quantum optics. Simply sweeping the gate-voltage bias achieves arbitrary Fock-state pulsed maser, where the single qubit plays the role of artificial gain medium. Resonantly pumping the parametric qubit-resonator interface leads to the squeezing of resonator field, which is utilizable to the quantum-limited microwave amplification. Moreover, upwards and downwards multiphoton quantum jumps may be observed in the steady state of the driving-free system.

Relaxation of Rabi Dynamics in a Superconducting Multiple-Qubit Circuit

  1. Deshui Yu,
  2. Leong Chuan Kwek,
  3. and Rainer Dumke
We investigate a superconducting circuit consisting of multiple capacitively-coupled charge qubits. The collective Rabi oscillation of qubits is numerically studied in detail by imitating
environmental fluctuations according to the experimental measurement. For the quantum circuit composed of identical qubits, the energy relaxation of the system strongly depends on the interqubit coupling strength. As the qubit-qubit interaction is increased, the system’s relaxation rate is enhanced firstly and then significantly reduced. In contrast, the inevitable inhomogeneity caused by the nonideal fabrication always accelerates the collective energy relaxation of the system and weakens the interqubit correlation. However, such an inhomogeneous quantum circuit is an interesting test bed for studying the effect of the system inhomogeneity in quantum many-body simulation.

Superconducting Qubit-Resonator-Atom Hybrid System

  1. Deshui Yu,
  2. Leong Chuan Kwek,
  3. Luigi Amico,
  4. and Rainer Dumke
We propose a hybrid quantum system, where an LC resonator inductively interacts with a flux qubit and is capacitively coupled to a Rydberg atom. Varying the external magnetic flux bias
controls the flux-qubit flipping and the flux qubit-resonator interface. The atomic spectrum is tuned via an electrostatic field, manipulating the qubit-state transition of atom and the atom-resonator coupling. Different types of entanglement of superconducting, photonic, and atomic qubits can be prepared via simply tuning the flux bias and electrostatic field, leading to the implementation of three-qubit Toffoli logic gate.