Qudit

In quantum computing, a qudit (/ˈkjuː/dɪt/) or quantum dit is the generalized unit of quantum information described by a superposition of d states, where the number of states is an integer equal to or greater than two.

Qudit versus qubit

A qudit, characterized by d=2 states is a qubit .<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Qudits with d states greater than 2 can provide a larger Hilbert space, providing more ways to store and process quantum information.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Qudit States

• Qubit - Qudit with d=2 states

• Qutrit - Qudit with d=3 states

• Ququart - Qudit with d=4 states

Error Correction

Quantum decoherence is the natural process where quantum information is lost due to environmental interaction and quantum error correction is a technique that actively combats decoherence.

In a paper published September 2025, researchers demonstrate a new hybrid method that encodes information in both light and matter using a cat state qudit with d>2 which allows for the detection of photon loss through the parity syndrome by entangling a light pulse with ancillary qubits. This method achieves parallel Bell-pair generation by leveraging the multi-level nature of the qudit.<ref>Template:Citation</ref>

Qudit Logic Gates

A qudit logic gate (or simply qudit gate) is a basic quantum circuit that acts on a qudit.

To achieve a universal qudit gate, (a gate that can be used to approximate any unitary transformation on a quantum computer to an arbitrary degree of accuracy) a set of gates must include a finite set of single qudit gates and at least one two qudit entangling gate that can create entanglement between qudits.

Use In Measurement

Quantum information is traditionally used in Ramsey interferometry, a technique used for precise measurement across various areas of science and technology.

Qudits with d>2 have shown to increase precision and resolution of quantum measurements. Qutrits, for example, have shown to achieve a twofold increase in resolution compared to qubits without any reduction in measurement contrast.<ref>Template:Citation</ref>

References

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