The D-Wave QPU is a lattice of interconnected qubits. While some qubits connect to others via couplers, the D-Wave QPU is not fully connected. Instead, the qubits interconnect in an architecture known as *Chimera*.

The Chimera architecture comprises sets of connected *unit cells*, each with four horizontal

qubits connected to four vertical qubits via couplers. Unit cells are tiled vertically and

horizontally with adjacent qubits connected, creating a lattice of sparsely connected qubits.

The notation *CN* refers to a Chimera graph consisting of an NxN grid of unit cells. The

D-Wave 2000Q QPU supports a C16 Chimera graph: its 2048 qubits are logically mapped

into a 16x16 matrix of unit cells of 8 qubits.

In a D-Wave QPU, the set of qubits and couplers that are available for computation is

known as the working graph. The yield of a working graph is typically less than the total

number of qubits and couplers that are fabricated and physically present in the QPU.

**See also: **What is the QPU Working Graph?

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