Synchronization

In this section, we explain how to synchronize multiple instruments in your setup including Qblox instruments. Synchronization is based on two aspects:

1. A shared reference clock, preferably phase aligned, so that all instruments use the same reference to base their operations on.

2. A synchronized start event, so that all instruments start their operations simultaneously.

The following subsections will go into more detail on how to achieve both aspects. This page considers the external connections on the Cluster Management Module and the connections inside the mainframe. For convenience, the image of the CMM front panel as well as the block diagram of the Cluster backplane are shown below.

Front panel of CMM. Cluster backplane and CMM block diagram.

Reference clock

Like most instruments, the Qblox instruments use a 10 MHz clock as a time reference. To synchronize multiple instruments in your setup you will need to connect such a reference clock to the REFin SMA connector of the cluster CMM module (10 MHz, 1 Vpp nominal @ 50 Ω) (see section CMM module) and set the reference_source() parameter to external. Connecting the reference can be done in two ways:

1. Through a clock distribution module that distributes a reference clock provided by a reference clock source to all instruments. Care has to be taken that all distributed reference clocks are length matched to keep the phase of the clocks aligned.

2. Through daisy-chaining the reference clock from one Qblox CMM module to the next. The Qblox instruments have been configured such that when a 50 cm coaxial cable is used to connect the REFout SMA connector of one instrument to the REFin SMA connector of the next, the instrument’s reference clocks are phase aligned to one another. This removes the need of an additional clock distribution module. The first instrument in the daisy chain can either use an internal reference source or an external reference if you wish to connect additional non-Qblox instruments. All other Qblox instruments need to be configured to use external reference sources.

SYNQ

To synchronize the start event of the instruments, Qblox SYNQ technology can be used to greatly simplify the process. All modules within a cluster share the same SYNQ network. Clusters can also be daisy-chained to each other to share the same SYNQ network. Additionally, the Sequencer.sync_en() parameter needs to be set for every sequencer in the instrument participating in the experiment and these same sequencers need to execute the wait_sync instruction (see section Instructions). Note that these last two steps also need to be executed when only using a single Qblox instrument. The Qblox SYNQ technology will then automatically align the timing of every participating sequencer in all Qblox instruments to within 300 ps of one another.

Trigger

If desired, the Qblox instruments can also be triggered by other instruments using an external trigger signal. To achieve this, simply connect the external trigger signal to the TRIGin SMA connector (0-3.3 V, high-Z). Then follow the instructions in the External trigger input section to configure the external trigger input. Any sequencer in the Qblox instrument can then synchronize to the experiment by executing the wait_trigger instruction (see section Instructions).

Markers

Additionally, the marker output channels can be controlled by the sequencers using the set_mrk instruction to trigger other instruments, thereby synchronizing them with the Qblox instruments (see section Instructions). However, care needs to be taken to compensate for any trigger delay caused by the connection or the triggered instrument itself.