In this chapter, we provide a brief overview of the functionality of the
Session class. A Session is the fundamental way to interact with
physical and emulated devices within the LabOne Q framework. This class
represents a single client session to a data server, which manages the
communication between the user PC and the instruments in the QCCS
system. For a more detailed description of the architecture, we refer
the reader to the LabOne user
In the context of LabOne Q, the
Session can be defined using a
and takes care of verifying the availability of the instruments
described by this class.
As the main endpoint for the user interaction with the QCCS, a session
object holds information about the physical wiring of the devices and
their calibrations properties,
information about the experiment definition that can be run on the
devices, and the results of executed experiments.
## define Session object
session = Session(device_setup=device_setup)
## connect the Session
Using this class it is possible to run experiments, compile experiments without running them, adjust the level of logs produced during execution, and much more.
## compile an experiment without running it
## set log level to debug
session.log_level = logging.DEBUG
## run the experiment
A complete list of the functionalities of this class can be found in the API documentation.
Session can be run in
emulation mode by connecting with the corresponding
No actual connection to the physical devices is attempted in this case.
## connect the Session in emulation mode)
Note, that the compiler still produces code consistent with the
requirements of the devices within that
The emulation mode of the
Session therefore serves to test the compilation and -to
some extent- execution of experiments without using the actual instruments.
A successfully executed experiment will produce arrays with axes corresponding to the
sweeps, averaging and data acquisition settings of the experiment.
These arrays contain complex mock-up data for debugging purposes
A + j*B
A of this mock-up data corresponds to
42 plus the index of the
integrator unit assigned to the particular channel of the emulated QA device where the
experimental signal is mapped to. This means that for typical settings where signals
from multiple qubit readouts are multiplexed into one channel, this index will
correspond to the qubit index.
The complex component
B indicates the index in the data array.
Reusing an Active Session¶
Session object needs a few seconds to establish the initial communication to the instruments connected to the dataserver.
Repeatedly initializing new
Session objects can therefore lead to a significant time overhead and should be avoided.
An initialized and connected
Session object is intended to compile and execute all experiments of a given workflow.
Instead, an active
Session object can compile and run multiple different experiments.
## run the first experiment (compilation happens implicitly)
## compile the second experiment
compiled_exp2 = session.compile(exp2)
## run the second experiment
Zurich Instruments Toolkit¶
As the fundamental class for the instrument interface, a
be used to control individual devices and node values. This is performed
address a specific device contained in the
Using Toolkit functions is not possible if the
was created in
emulation mode, as it is impossible to address physical
nodes without connecting to an instrument.
- When LabOne Q controls devices by running an experiment via
session.run(), never use subscribe/poll over
zhinst.toolkit(neither in the main script before/after
session.run(), nor in the near-time callbacks)
- When working solely with the
zhinst.toolkitand only getting the initial connection via LabOne Q session, use subscribe/poll as you need it.
To address a device, we can use its uid as defined in the
and then using a toolkit command to change a specific node.
## connect to the session
## change the amplitude of channel 1 to 1 V
A device can also be addressed using its serial number instead of its
uid. Using this descriptor,
for example, we could substitute
produce an identical result.
Using this functionality, a
Session can be used to change, or even
sweep, a node of a device inside an
Experiment definition, as
described in the chapter Callback Functions and 3rd-Party
Note that this can only be done in near-time.