We’ll talk about the introduction of Cat Qubit quantum computing in this blog, as well as what Cat Qubits are.
Cat Qubits
The name “cat qubits” comes from Schrodinger’s cat and quantum physics. The famous thought experiment involves a living-dead cat. Similarly, a cat qubit exists in two quantum states simultaneously, although in actuality it is different from the fictional cat.
One amplitude and one phase are encoded by a standard superconducting qubit. The quantum state can be either +α or -α, but not both, if the encoded amplitude is α. One sort of superconducting qubit, the cat qubit, differs in that it encodes the same amplitude twice, but with opposite phases. In other words, the cat qubit is comparable to Schrodinger’s notorious cat since it exists simultaneously in the states +α and -α. There is always one amplitude with two opposing phases in the cat spectrum.
The ScienceDirect article “Cat-qubits for quantum computation” offers a thorough technical analysis of cat qubits. Try reading the ScienceDaily article “Schrödinger’s cat makes better qubits” for a more sophisticated explanation.
Cat Qubit quantum computing
What Are Cat Qubits?
Superconducting qubits known as “cat qubits” provide an uneven trade-off between bit flip and phase flip error rates. Cat qubits trade off an exponential drop in bit flip error rates and a linear increase in phase flip error rates, in contrast to superconducting qubits, which typically experience both bit flip and phase flip mistakes at high rates. The slight penalty in phase flip error rates is thought to be justified by the substantial improvement in bit flip error rates.
The usual overhead of quantum error correcting codes (QECC) is the reason this compromise is acceptable. Fault-tolerant quantum computing (FTQC) requires a large number of physical qubits to encode logical qubits with low enough error rates. Cat qubits suggest utilising far fewer physical qubits per logical qubit in order to achieve the same low error rates as other superconducting qubits. This should make FTQC one step closer to reality, assuming everything else stays the same.
Theoretical Foundations of Cat Qubits
The theoretical underpinnings of quantum error correction (QEC) and superconducting qubits are combined in the theory of cat qubits. The following are the fundamentals of cat qubits:
- A cat qubit is always in a superposition of two quantum states, in contrast to a superconducting qubit, which is always in a single quantum state, a superposition of 0 and 1.
- Cat qubits exponentially suppress bit-flip errors, as if integrating a self-correcting QEC code; similar to QECC, this requires a trade-off.
- While cat qubits unevenly trade off lower bit flip error rates and larger phase flip error rates, QECC trades off lower error rates and greater physical qubit counts.
- By combining active QEC with the passive QEC of the cat qubits, the ratio of physical qubits to logical qubits can be decreased, shortening the road to FTQC.
- It is possible to implement transversal gates, also known as logical gates, that prevent bit-flip errors from being reintroduced into the logical qubits that make up the cat qubits.
It is important to note that cat qubits are still primarily theoretical. Currently, there are no superconducting quantum computers with cat qubits that are accessible to the general public.
Cat Qubit Experimental Implementations
However, cat qubits are not totally theoretical. Several cat qubit concepts have already been proven through experimentation:
- Compared to other superconducting qubits, cat qubits have shown bit-flip times of over 10 seconds, which is a considerable amount of time.
- The above can be confirmed using a quantum tomography procedure that doesn’t introduce bit-flip errors into the qubits.
There have already been proposals for QEC codes that would fully utilize these characteristics. FTQC should ultimately require significantly fewer physical qubits than other superconducting qubits.
Important details regarding cat qubits
Error correction advantage
Because cat qubits encode information in a fashion that makes bit-flip errors exponentially less likely to occur, they are especially successful at reducing bit-flip mistakes, which are frequent in standard qubits.
Superposition principle
As the foundation for the error protection mechanism of cat qubits, the “cat state” is a quantum superposition in which a qubit is concurrently in both the “0” and “1” states.
Trade-off with phase flip errors
Cat qubits may have a slightly higher rate of phase flip errors while drastically lowering bit-flip errors, but this is sometimes regarded as a worthwhile trade-off because of the enormous gain in bit-flip error correction.
Research focus
With the goal of using their error-correction capabilities to create more reliable and scalable quantum computers, businesses such as Alice & Bob are actively investigating and developing cat qubit technology.
