Scalable Realization of Surface Code Quantum Memory by Applying Multi-Qubit Parity Detector Gates

  1. Sahar Daraeizadeh,
  2. Sarah Mostame,
  3. Preethika Kumar Eslami,
  4. Marek Perkowski,
  5. and Xiaoyu Song
We analytically designed the control bias pulses to realize new multi-qubit parity detector gates for 2-Dimensional (2D) array of superconducting flux qubits with non-tunable couplings.
We designed two 5-qubit gates such that the middle qubit is the target qubit and all four coupled neighbors are the control qubits. These new gates detect the parity between two vertically/horizontally coupled neighbor qubits while cancelling out the coupling effect of horizontally/vertically coupled neighbor qubits. For a 3 by 3 array of 9 qubits with non-tunable couplings, we simulated the effect of our new 5-qubit horizontal and vertical parity detector gates. We achieved the intrinsic fidelity of 99.9% for horizontal and vertical parity detector gates. In this paper we realize Surface Code memories based on the multi-qubit parity detector gates for nearest neighbor superconducting flux qubits with and without tunable couplings. However, our scheme is applicable to other superconducting qubits as well. In our proposed memory realization, error correction cycles can be performed in parallel on several logical qubits or even on the entire 2D array of qubits, this makes it a desirable candidate for large scale and longtime quantum computation. In addition to extensive reduction of the number of control parameters in our method, the error correction cycle time is reduced and does not grow by increasing the number of qubits in the logical qubit layout. Another advantage of this approach is that there will not be any dephasing from idle qubits since all the qubits are used in the error correction cycles.

Towards Outperforming Classical Algorithms with Analog Quantum Simulators

  1. Sarah Mostame,
  2. Joonsuk Huh,
  3. Christoph Kreisbeck,
  4. Andrew J. Kerman,
  5. Takatoshi Fujita,
  6. Alexander Eisfeld,
  7. and Alán Aspuru-Guzik
With quantum computers being out of reach for now, quantum simulators are the alternative devices for efficient and more exact simulation of problems that are challenging on conventional
computers. Quantum simulators are classified into analog and digital, with the possibility of constructing „hybrid“ simulators by combining both techniques. In this paper, we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators.

Quantum simulator of an open quantum system using superconducting qubits: exciton transport in photosynthetic complexes

  1. Sarah Mostame,
  2. Patrick Rebentrost,
  3. Alexander Eisfeld,
  4. Andrew J. Kerman,
  5. Dimitris I. Tsomokos,
  6. and Alán Aspuru-Guzik
Open quantum system approaches are widely used in the description of physical, chemical and biological systems. A famous example is electronic excitation transfer in the initial stage
of photosynthesis, where harvested energy is transferred with remarkably high efficiency to a reaction center. This transport is affected by the motion of a structured vibrational environment, which makes simulations on a classical computer very demanding. Here we propose an analog quantum simulator of complex open system dynamics with a precisely engineered quantum environment. Our setup is based on superconducting circuits, a well established technology. As an example, we demonstrate that it is feasible to simulate exciton transport in the Fenna-Matthews-Olson photosynthetic complex. Our approach allows for a controllable single-molecule simulation and the investigation of energy transfer pathways as well as non-Markovian noise-correlation effects.