← All parts of this equation

Equation 14 · Part 1 · Error Correction Is the Whole Problem in Quantum Computing

Symbol n_phys

nphys=2d2−1,n_{\mathrm{phys}} = 2d^{2} - 1 ,
nphysn_{\mathrm{phys}}

What this part means

the physical cost of one logical qubit.

Its job in the formula

npn_phys is part of the quantity the equation computes from the expression on the right.

Where the article explains it

For the planar surface code in its standard rotated layout, the physical cost of one logical qubit is

The passage around this formula

Distance d is the weight of the smallest undetectable logical error. A distance- d code corrects up to ⌊\lfloor (d-1)/2 ⌋\rfloor errors. For the planar surface code in its standard rotated layout, the physical cost of one logical qubit is nphys=2d2−1n_{\mathrm{phys}} = 2d^{2} - 1 . counting data and measure qubits together. A distance-7 patch therefore occupies ninety-seven physical qubits, and that is a memory holding one logical qubit, doing nothing else. It performs no gate, produces no non-Clifford operation, and reserves no routing space.

Read this part in the article →

Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

See this notation across published equations →

The article lists its research sources here.