Josephson Junction Qubits

The central objective of workpackage-1 is to design, fabricate and characterise quantum registers with Josephson junction-based qubits. The goal is to establish the state of the art in qubit coherence, readout, coupling and scalability. To that end, we are exploring and developing different qubit designs including transmons, phase and flux qubits. To achieve coupling and scalability, we are exploring the use of on-chip microwave cavities that will act as a quantum information bus as depicted on the figure below.

We anticipate that these quantum buses will enable the controlled coupling of remote qubits as well as the conversion of quantum information from fixed qubits to flying qubits (microwave photons) that can be used to distributed entanglement.  In close interaction with the hardware progress, the software goal is to develop and implement protocols and algorithms that make maximal use of the available hardware to achieve universal gate operations, control of multi-qubit entanglement, benchmark algorithms and protocols, implement elementary error-correction, and test elementary control via quantum feedback.

Workpackage 1 is led by chris [dot] wilson [at] chalmers [dot] se (subject: MAIL%20FROM%20SOLID%20WEBSITE%20RE%3A%20WP1) (Chris Wilson) from Chalmers and progress is measured against the the following eight milestones:

• M1.1 Characterisation and operation of multi-qubit registers (3-6 qubits) with readout of individual qubits coupled through a common oscillator bus. 
• M1.2 Multi-qubit platforms: single-shot QND readout of individual qubits. 
• M1.3 Quantitative determination of readout fidelities for 1- and 2-qubit readout for multi-qubit platforms.
• M1.4 Several platforms will achieve readout fidelity of >> 90% for a single qubit. 
• M1.5 Preparation, readout and tomography of states with 2-4 entangled qubits. 
• M1.6 Demonstration and tomographic characterization of universal gate operation on multi-qubit platforms. 
• M1.7 Experimental implementation of algorithms and protocols on multi-qubit platforms (Bell mesurements; teleportation; coding; Grover; Deutsch-Jozsa; Iterative Phase Estimation. 
• M1.8 Design of a toolbox of resonant two-qubit gates.