What's the drawback of bosonic qubits/codes?

[quantumadmin]

Bosonic qubits and codes, often referred to as "bosonic quantum error correction" or "continuous-variable quantum error correction," are a type of quantum error correction approach that uses bosonic modes of a quantum field, such as photonic modes, to encode and process quantum information. While this approach has some advantages, it also comes with certain drawbacks and challenges:

Vulnerability to Loss and Noise: Bosonic qubits are particularly sensitive to loss and noise due to their continuous-variable nature. Noise can lead to the degradation of quantum information encoded in bosonic modes, making error correction challenging.

Gaussian Operations: Many bosonic quantum error correction codes rely on Gaussian operations, which are linear transformations that preserve the Gaussian nature of quantum states. However, Gaussian operations have limitations in terms of their ability to correct certain types of errors and protect against more complex noise sources.

High Overhead: Implementing error correction for bosonic qubits can require a high overhead in terms of additional resources, such as ancillary qubits or modes and extra gates. This overhead can limit the scalability and practicality of implementing complex quantum computations.

Limited Gate Set: The set of gates that can be implemented directly on bosonic qubits is limited compared to discrete-variable qubits like superconducting qubits. This can restrict the types of quantum operations that can be performed and the range of algorithms that can be executed.

Non-Gaussian Noise: While many quantum error correction codes for bosonic qubits focus on correcting Gaussian errors, non-Gaussian noise sources can pose challenges. These non-Gaussian errors might require more sophisticated error correction techniques that are currently under development.

Verification and Measurement Challenges: Measuring and verifying quantum information in bosonic qubits can be technically demanding due to the continuous-variable nature of the encoding. Achieving accurate and reliable measurements is crucial for error correction but can be challenging.

Decoding Complexity: The process of decoding the quantum information from bosonic codes after error correction can be computationally intensive and complex. Efficient decoding algorithms are required to manage the intricacies of continuous-variable error correction.

Compatibility with Hardware: Integrating bosonic qubits and error correction with existing quantum hardware architectures, which often use discrete-variable qubits, can pose challenges and may require additional engineering efforts.

Despite these challenges, research into bosonic qubits and continuous-variable quantum error correction continues to advance, and they may find applications in specific scenarios where their unique properties are advantageous. Overcoming the limitations and drawbacks of bosonic qubits is an active area of research in the field of quantum information processing.