Figure 2 : The encoding circuits of the 2WNC-assisted QECCs (a). and (b). .

From: Quantum error correction assisted by two-way noisy communication

Figure 2

A boxed H represents a Hadamard gate, a pair of connected black dots represents the controlled-phase gate UCP, a pair of connected black (source) and white (target) dots represents a controlled-NOT gate UCN, and . The dotted lines represent noisy quantum channels.