What Are Grid States? Why It Is Important & How It Prepared?
What's Grid States? Grid states embed logical qubits into harmonic oscillators like microwave cavities or trapped ions. They are sometimes called Gottesman-Kitaev-Preskill (GKP) code states.
Theoretical ideals generate lattice structures. They are an infinite superposition of position eigenstates, which is impractical due to their unlimited energy needs. They are represented as an endless grid of sharp points in phase space, which conveys position and momentum. The approximate (or physical) grid states are finite-energy versions of these states that can be made in a lab. Instead of infinite sharp points, they have a finite number of “squeezed states”. Although these states' points are not indefinitely sharp, they exhibit a grid-like phase space pattern. Quality approximation states are needed for practical usage. Its lattice structures include square, rectangular, and hexagonal. Why it Matters? Grid states are essential to building a fault-tolerant quantum computer. Grid states' main function is quantum error correction (QEC). Due of noise sensitivity, quantum computers make mistakes. Quantum Error Correction (QEC) systems encode quantum data using grid states to protect it from noise. Non-local encoding allows defects to be recognised and rectified over time because noise in one location doesn't immediately skew logical information. Hardware Efficiency: Grid states can encode a qubit into a single oscillator, making it hardware-efficient compared to employing multiple physical qubits. Resilience: Grid states allow the GKP algorithm to detect and fix minor oscillator displacement issues. It also performs well against boson loss, or oscillator particles, often outperforming specially designed algorithms. The hexagonal GKP coding may mitigate this loss best. In addition to quantum computing, GKP codes and grid states may be used in quantum metrology and sensing. How are Grid States Ready? Noise from the technique makes grid state preparation harder. Several protocols have been implemented to manufacture them. Qubit interaction Combining a qubit with the oscillator is a common method. This can be done with superconducting microwave cavities or trapped ions. Methods based on measurements Early and modern experiments measure the auxiliary qubit repeatedly. The grid state is created using these metrics and feed-forward or post-selection. Due to the long duration of these experiments, noise might degrade the fragile quantum state. Measurement-free approaches Researchers developed measurement-free preparation approaches to speed up and improve state quality. These methods use Rabi interactions between the oscillator and qubit to deterministically produce the grid state without measuring the qubit. By eliminating slow measurements, these methods provide higher-quality grid states faster. Starting Point The grid structure is often built from a “squeezed vacuum state” and several interactions. Final grid state quality depends on initial compressed state quality. Differentiating States These techniques may generate hexagonal and rectangular lattices as well as the fundamental grid states.