Extended register forwarding

In this example, there are two QA channels writing their readout results in register 1 and 29 respectively. The PQSC is configured to forward eight results to two different instruments connected to the first two ZSync ports, as shown in Figure 1. When a QA performs a readout, its results are automatically written in the readout register specified in the fourth argument of the startQA command, and the PQSC automatically forwards the chosen results.

To configure the PQSC as in Figure 1, its nodes should be programmed as in Table 1.

The instruments receive a word from the data sources configured in the PQSC. Such words contain the output of both the register forwarding and the error decoder unit. The conditional instruction, either getFeedback or executeTableEntry, should specify the source of feedback with the constant ZSYNC_DATA_PQSC_REGISTER or ZSYNC_DATA_PQSC_DECODER to select the relevant portion of the message. The constant ZSYNC_DATA_RAW provides the full message without any processing. Each sequencer in the instrument can reduce the message to the portion that is relevant for it; for example the state of a qubit to reset. This is done by binary shift and masking. An optional additive offset could be added. In Figure 2 an example of the flow of data to reset four qubits connected to a SHFSG4 is provided.

In order to enable such processing, the instrument nodes should be configured as in Table 2.

With such settings, each sequencer can get its processed feedback in a variable with var feedback = getFeedback(ZSYNC_DATA_PQSC_REGISTER) or directly play a conditional pulse with executeTableEntry(ZSYNC_DATA_PQSC_REGISTER).

Like in the previous example, there are two QA channels writing their readout results in register 1 and 29 respectively. QA1 is configured such that two results (X and Y) are the output of Multi State Discrimination (MSD), so each is composed by two bits, while another (Z) is the result of regular discrimination, so it uses only one bit. The QA2 produces three results (I,J and K) from regular discrimination, so a total of three bits. The PQSC is configured to forward these results to two different instruments connected to the first two ZSync ports, as shown in Figure 1. A third instrument is configured to receive the output of the decoder unit. For clarity in this example, the register forwarding is sending only three results per port instead of the maximum of eight and the configuration of the decoder unit is omitted.

To configure the PQSC as in Figure 3, its nodes should be programmed as in Table 3.

Like in the previous example, each sequencer in the instrument can reduce the message to the portion that is relevant for it by binary shift and masking. In Figure 4, there is an example of the flow of data of the SHFSG8 connected to the first ZSync port of the PQSC; it reset three qubits (channels 2 and 3) and one qutrit. Similarly, in Figure 5, the same goes for the SHFSG8 connected to the second ZSync port of the PQSC.

In order to enable such processing, the instrument nodes should be configured as in Table 4 and Table 5. It should be noted that the shift is still expressed in bits, not couples of bits like in the register selector of the PQSC. This allows for finer granularity in the selection of the interesting portion of the message. It also allows for the execution of feedback on a single bit, even if the PQSC register forwarding unit sent two bits, like in channel 2 and 3 of the first SHFSG.

Like before, the sequencers can acquire their feedback in a variable with var feedback = getFeedback(ZSYNC_DATA_PQSC_REGISTER), or directly play a conditional pulse with executeTableEntry(ZSYNC_DATA_PQSC_REGISTER), so no changes there.