Quantum Computation … and Akbar?

By Jibran Rashid


At Habib, our undergraduate students are not only allowed, but also expected, to contribute to cutting edge problems in faculty project. This is exemplified in Dr. Jibran’s informal quantum information and computation discussion group, where students are introduced to fundamental quantum concepts such as non-locality and entanglement.

The deal with quantum

A ball thrown at a wall returns to its origin with velocity equal in magnitude but opposite in direction (assuming an ideal setup). In other words the direction or sign associated with the velocity in the beginning and at the end is anti-correlated. This is a direct consequence of the laws of physics. In essence these laws serve as a fundamental guiding principle through which we derive physical consequences such as the correlations above. The example may seem mundane given that such correlations are part of our every day experience. The intriguing nature of correlations produced by quantum physics (known as nonlocality) however defy such an intuitive explanation. In order to obtain a better appreciation of this quantum behaviour let us take a historical detour …
The Power of Informed Advice:
The advisor Birbal has a new lesson for the Mughal Emperor Akbar. Birbal suspects that since his accession to the throne Akbar has grown too dependent on his judgement and does not heed the advice of those around him. He intends to show Akbar the folly of his way by demonstrating that tasks which may seem impossible are made possible by reliance on a trustworthy and well-informed ally. To achieve this end, Birbal cooks up the following task for Akbar. Akbar is free to choose any question which is answerable by a simple `YES’ or ` NO’. The catch is that the information required to answer the question is not known to Akbar. The information is distributed between two of Akbar’s viziers in such a way that neither has complete information required to answer Akbar’s question. Given the political intrigue in the court the viziers do not trust each other or even Akbar with their share of information. The task for Akbar then is to figure out a way to obtain an answer to his question while burdened by these restrictions.
Try as he may, Akbar is unable to resolve this conundrum and finally resorts to seek advice from his favourite advisor. Birbal asks permission to act as an advisor to both the viziers from whom Akbar seeks the answer. He secretly dispatches individual set of instructions to Akbar and both the viziers. Birbal guarantees that if his instructions are followed, the outcome will satisfy everyone, i.e.,

  1.  Birbal does not learn either Akbar’s question or the secret information of each vizier required to
    answer the query.
  2. Akbar does not learn the secret information of each vizier required to answer his question.
  3. Neither of the two viziers learn each other’s secret information.
  4. Akbar learns the answer to his question.

Akbar’s scepticism of Birbal’s claim gives way to wonder as he witnesses the instructions in action again and again. Repeating Akbar’s instructions multiple times with a different set of questions and viziers finally convinces Akbar that Birbal’s instructions work. So what exactly were Birbal’s  instructions? To find out visit our quantum computation class!