Quantum Bayesian Networks

January 1, 2018

New tools for dealing with limited couplings of a quantum computer chip

Filed under: Uncategorized — rrtucci @ 11:37 pm

The main purpose of this blog post is to announce that Qubiter now has two simple, but hopefully useful, new classes that facilitate writing qc programs for the new crop of qc’s with 20-50 qubits but such that those qubits are not fully connected (coupled):

  1. Class ForbiddenCNotExpander reads an English file and writes a new English file. Any CNot in the old file that is not physically allowed by a pre-specified qc chip is replaced in the new file by an expansion (sequence) of allowed CNots.

  2. Class ChipCouplingsFitter reads an English file and writes a new English file. The new file permutes the qubits of the old file so that the old CNots are mapped into new ones that are allowed for a pre-specified qc chip. Of course, this is not always possible, so the class only promises to find such a mapping and to tell you what it is if it finds one.

I hope these 2 new classes will make it easier for Qubiter users to interact with real qc hardware of any brand.

We are striving to make Qubiter interact with as many qc hardware brands as possible. So far, we have targeted the IBM chips with a class called Qubiter_to_IBMqasm2 that translates a Qubiter English file (i.e., Qubiter’s version of qasm) to IBM qasm2. As soon as Google comes out with its 49 qubit qc and accompanying cloud service, which Martinis has promised for Jan 2018, we will target Google devices too, by writing a translator from Qubiter English files to Google’s version of qasm. This IBM or Google qasm can be sent by a Jupyter notebook via the internet to the IBM or Google quantum computers sitting in the cloud, which will then run the program and send back the results to the original Jupyter notebook.

We are trying to design Qubiter so that it facilitates communication not only between a user and multiple hardware devices, but also among multiple users. Indeed, Qubiter already makes it easy for users of different qc devices, for example Alice who uses an IBM chip and Bob who uses a Google chip, to be on friendly terms with each other, maybe even go out on a date. Qubiter facilitates such dalliances because it saves quantum circuits as simple yet clear text files. This makes it as easy as pie to modify those text files, save them to improve them at a later date, and share them with other qc engineers. I you want to collect quantum circuits like you would collect baseball cards, comic books, stamps, butterflies or whatever, Qubiter’s English and Picture files found in Qubiter’s io_folder are a great way of doing it.



  1. Graphic reminds me also of ordeal of Romeo Montague and Juliet Capulet.

    Comment by rrtucci — January 2, 2018 @ 4:54 am

  2. Awesome!
    And awesome graphic as well ^_^

    Comment by yintaophy — January 2, 2018 @ 2:06 pm

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