Ion traps Quantum Computer Innovation Center Hamburg
Contractor

Objective

We are developing a fully scalable trapped-ion quantum computer that interconnects four quantum computing modules.

One path leading to the realisation of quantum computers with millions of qubits is to develop a basic module that can perform all the essential quantum operations and then connect many such modules together. Using this approach, we will build a fully scalable trapped-ion quantum computer for the DLR Quantum Computing Initiative that will connect four quantum computing modules. These modules are based on silicon semiconductor chip technology and are being used in the QCI project Toccata. Initially, we will design modules with at least ten qubits and interconnect at least two modules. However, the design can accommodate more than 25 qubits and scale up to a networked system with at least 100 qubits. To do this, we will connect the modules using electrical field interconnects with sufficient performance for fault-tolerant quantum computing.

Motivation

Since a single ion-trap wafer can contain at most a few hundred qubits, modularity is crucial for realising trapped-ion quantum computers with millions of qubits. The interconnection of individual quantum computer modules is often described as one of the biggest problems in this regard. Our solution to this is UQConnect, with which we can establish electric field connections between neighbouring modules at – compared to other approaches – much faster connection speeds and using simpler technology. Despite this, we still achieve sufficient performance for fault-tolerant quantum computing. This enables the scaling necessary to work towards the execution of quantum gates in quantum computers with millions of qubits.

Challenge

We solve the problem of interconnectivity using electric field connections between neighbouring quantum computing modules. We call this approach UQConnect. It enables connection speeds that are orders of magnitude faster than other methods. Despite this, it utilises much simpler technology. For example, in an experimental demonstration of UQConnect, we were able to realise coherent transport of a qubit between two neighbouring modules with a connection rate of 2424 connections per second and a transmission fidelity of 99.999993 percent. For the execution of quantum gates, we use our global-field technology. The advantage is that the number of microwave fields required remains the same, even if the number of qubits is increased. In addition, while in many other quantum computing approaches the chip has to be cooled almost to absolute zero, our technique works with mild cooling to approximately minus 200 degrees Celsius, which significantly improves the design and reliability of the system.




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