When I run
ibmqx2 is listed as an available backend, but is not listed on the IBMQ systems page. This file from the archived repository ibmq-device-information associates backend name
ibmqx2 with display name IBM Q 5 Yorktown. The IBMQ systems page does list a 5 qubit Yorktown device, but under the name ibmq_5_yorktown. This backend is also available via
ibmq/open/main, but is not listed by
ibmq_5_yorktown respectively versions 1 and 2 of backend software providing access to a single Yorktown device? Or do these names refer to two distinct Yorktown devices?
When I run
ibmqx2 and Yorktown are one quantum processor. When IBM Quantum platform was released, two processors - Yorktown and Tenerife were available. These processor were denoted also
ibmqx4, respectivelly. Note that Tenerife processor is retired now.
If you have a look into IBM Quantum environment, you can see that there is
ibmqx2 processor in list of available devices. See here:
When you click on
ibmqx2, this page is shown:
So, it means that
ibmqx2 and Yorktown are identical devices.
The naming is just a legacy of former times.
I would be happy if anybody from IBM can add more comments.
As @Martin Vesely answered, it is the same device.
Here is the README documentation showing that they are the same: https://github.com/Qiskit/ibmq-device-information/blob/master/backends/yorktown/V1/README.md
Here is a little screen shot of that documentation: