[Paper Review] Hybrid Qubit gates in circuit QED: A scheme for quantum bit encoding and information processing

M. C. de Oliveira|arXiv (Cornell University)|Oct 6, 2011

Quantum Information and Cryptography28 references3 citations

TL;DR

This paper proposes a hybrid two-qubit gate in circuit QED that encodes quantum information in a photonic field mode of a coplanar transmission line, coupled to a single superconducting charge qubit. The scheme leverages the field's resilience to dissipation for robust quantum information storage, while enabling entanglement generation between multiple solid-state qubits and the field qubit via external classical magnetic pulses, offering a scalable, experimentally feasible architecture for quantum computation.

ABSTRACT

Institute for Quantum Information Science, University of Calgary, Alberta T2N 1N4, Canada(Dated: October 7, 2011)Solid state superconducting devices coupled to coplanar transmission lines offer an exquisite architecturefor quantum optical phenomena probing as well as for quantum computation implementation, being the objectof intense theoretical and experimental investigation lately. In appropriate conditions the transmission lineradiation modes can get strongly coupled to a superconducting device with only two levels -for that reason calledartificial atom or qubit. Employing this system we propose a hybrid two-quantum bit gate encoding involvingquantum electromagnetic field qubit states prepared in a coplanar transmission line capacitively coupled to asingle charge qubit. Since dissipative effects are more drastic in the solid state qubit than in the field one, itcan be employed for storage of information, whose efficiency against the action of an ohmic bath show that thisencoding can be readily implemented with present day technology. We extend the investigation to generateentanglement between several solid state qubits and the field qubit through the action of external classicalmagnetic pulses.

Motivation & Objective

• To develop a scalable quantum computing architecture using hybrid qubit encoding in circuit QED.
• To address the challenge of decoherence in solid-state qubits by leveraging the greater resilience of photonic field modes.
• To enable entanglement between multiple superconducting qubits and a field qubit using external classical magnetic pulses.
• To demonstrate that the proposed encoding scheme is implementable with current experimental technology.

Proposed method

• Utilizes a coplanar transmission line to host a quantum electromagnetic field qubit, capacitively coupled to a single superconducting charge qubit.
• Employs strong coupling between the transmission line's radiation modes and the artificial atom (qubit) to enable coherent quantum operations.
• Exploits the field qubit's superior resistance to ohmic dissipation compared to the solid-state qubit for information storage.
• Applies external classical magnetic pulses to mediate entanglement between multiple solid-state qubits and the field qubit.
• Designs the system such that the field qubit acts as a robust quantum memory, while the charge qubit enables gate operations.
• Relies on circuit QED architecture with superconducting devices and transmission line resonators to realize the hybrid gate.

Experimental results

Research questions

• RQ1 Can a hybrid two-qubit gate be implemented using a photonic field qubit and a single charge qubit in circuit QED?
• RQ2 How does the field qubit's resilience to ohmic dissipation improve quantum information storage compared to solid-state qubits?
• RQ3 Can entanglement be generated between multiple solid-state qubits and a field qubit using classical magnetic pulses?
• RQ4 Is the proposed encoding scheme feasible with current experimental technology in circuit QED?
• RQ5 What is the role of strong coupling between transmission line modes and the artificial atom in enabling the gate operation?

Key findings

• The photonic field qubit in the transmission line exhibits superior resistance to decoherence from an ohmic bath compared to the solid-state charge qubit, enabling robust quantum information storage.
• The hybrid gate scheme enables entanglement between multiple solid-state qubits and the field qubit through the application of external classical magnetic pulses.
• The proposed encoding method is compatible with existing circuit QED technology, making it readily implementable with current experimental setups.
• Strong coupling between the transmission line modes and the artificial atom allows for coherent quantum operations essential for quantum computation.
• The system design leverages the field qubit's stability to enhance overall gate fidelity and scalability of the quantum information processing architecture.