Example of Digital Analog Quantum Computing using Qadence. Credit: PASQAL

In quantum computing, there are two different types of modes that can be used to solve a problem. Digital mode is perhaps the more common mode and that implements quantum circuits via a series of gates that are applied to the qubits. The advantage of digital mode is that it is universal and can theoretically be used to solve any problem. The disadvantage of digital mode is that currently the gates are quite noisy so they likely require error correction and thousands of qubits and millions or billions of gates to provide quantum advantage. Analog mode on the other hand puts all the qubits in a register and lets them evolve continuously. So this mode is more tolerant of errors and can perform in one computational step what digital mode would require in thousands of steps. The disadvantage of analog mode, though, is that it is not universal and can only be applied to certain problems.

An interesting feature of neutral atom based quantum computers is that they can support both analog and digital mode. PASQAL has innovated with a new approach called Digital Analog Quantum Computing (DACC) that can use the two together to utilize the best features of each. They are providing an open-source Python library called Qadence to support this. The program configures the qubits into blocks. Single quantum gates can be applied to the qubits within a block and then the blocks are fed into an analog block that will evolve the quantum system continuously in a controlled fashion. Qadence can also be integrated with two other programming libraries developed by PASQAL including PyQTorch, a fast emulator for digital and digital-analog programs built on top of PyTorch, and Pulser, a pulse-level interface for programming neutral atoms devices.

More information is available about Qadence in a press release available here, a blog posting here, and the technical document which can be accessed here.

October 12, 2023