Exact quantum query algorithms

For the paper “Exact quantum query complexity of EXACT and THRESHOLD” by Andris Ambainis, Jānis Iraids & Juris Smotrovs; Maris Ozols, on his blog has posted an excellent analysis of this paper.

Mamuta memuāri

Andris Ambainis, Jānis Iraids, and Juris Smotrovs recently have obtained some interesting quantum query algorithms [AIS13]. In this blog post I will explain my understanding of their result.

Throughout the post I will consider a specific type of quantum query algorithms which I will refer to as MCQ algorithms (the origin of this name will become clear shortly). They have the following two defining features:

  • they are exact (i.e., find answer with certainty)
  • they measure after each query

Quantum effects in an MCQ algorithm can take place only for a very short time — during the query. After the query the state is measured and becomes classical. Thus, answers obtained from two different queries do not interfere quantumly. This is very similar to deterministic classical algorithms that also find answer with certainty and whose state is deterministic after each query.

Basics of quantum query complexity

Our goal is…

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First Hangout with Ronald de Wolf will speak on “Exponential Lower Bounds for Polytopes in Combinatorial Optimization” Sounds highly interesting. Perhaps we would see more ‘+’ of other fields as well!


You heard it here first — a new series of online seminars! For those of you who know, we got inspiration from the great Q+ seminars run by Daniel Burgarth and Matt Leifer.

Without further ado, here is the announcement:


Dear fellow TCSers,

Ever wished you could attend that talk — if only you didn’t have to hike the Rockies, or swim across the Atlantic, to get there; if only it could have been scheduled the following week, because this week is finals; if only you could watch it from your desk, or for that matter directly from your bed?

Starting this semester TCS+ will solve all your worries. We are delighted to announce the initiation of a new series of *online* seminars in theoretical computer science. The seminars will be run using the “hangout” feature of Google+. The speaker and slides will be broadcast live as well as…

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Quite Humorous!

Quantum Bayesian Networks

bogart-caine-mutiny-monologueA monologue from the film The Caine Mutiny (1954).

(Captain Queeg, a SUSY Theorist, removes the steel balls from his pocket and spins them insistently in his hands as he speaks.)

Queeg (Humphrey Bogart):
No, I, I don’t see any need of that. Now that I recall, he might have said something about messboys (messy theories) and then again he might not — I questioned so many men and Harding was not the most reliable officer.

Lt. Greenwald (Jose Ferrer):
I’m afraid the defense has no other recourse than to produce (experimentalist) Lt. Harding.

Now there’s no need for that. I know exactly what he’d tell you, lies. He was no different from any other officer (experimentalist) in the ward room, they were all disloyal. I tried to run the ship properly, by the book, but they fought me at every turn. The (CERN) crew wanted to walk…

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Decoy: LHC Horror Film

Finally finished watching the movie Decoy produced by group of physics PhD students of LHC and without a doubt I loved it. For a independent film it looks very much professional and from scientific point of view; way much better than other so-called science films. A must watch film.  For more check their websiteHD downloads or Youtube. I won’t spoil the film for anyone interested in watching but the film has scenes which shows LHC in new light.

Secondly, for those interested in non-fiction goodies check  Colliding Particles. It is a series of films following research in particle physics at the LHC

Finally Quantum Diaries has new post Advent Calendar 2012 December 7th which is about “spins”; Aidan Randle-Conde thinks that there is misunderstanding regarding the very term “spin”, the accompanying comments are also worth noting.

Good Bye to Year 2011

Year 2011 was indeed a year full of Exciting happening. From Arab Uprisings to Royal Wedding and to Assassination. But this year the field of Technology and Science in general heaved heavy loss of some of the greatest Pioneers passing away. This post is dedicated as a tribute to the persons who made a great impact of todays technology and Science :

Steve Jobs (February 24, 1955 – October 5, 2011) Apple Founder

Dennis MacAlistair Ritchie (September 9, 1941 – October 12, 2011) Founder of C & Co-Founder of UNIX

John McCarthy (September 4, 1927 – October 24, 2011) Pioneer of Artificial Intellegence (AI) & reciept of Turing Award

Robert William “Bob” Galvin (October 9, 1922 – October 11, 2011) Motorol Ex-CEO & pioneer of Six-Sigma

Gerald Anderson “Jerry” Lawson (December 1, 1940 – April 9, 2011) Video Game Developer

Robert Morris (July 25, 1932 – June 26, 2011) Cryptographer & Pioneer of Information Security

Paul Baran (1926–2011) Inventer of Packet Switching Technique & First Metal Detector

Anthony E. Siegman (1931–2011) Pioneer of Masers and Lasers.

Ralph Marvin Steinman (January 14, 1943 – September 30, 2011) 2011 Nobel Prize in Physiology or Medicine (posthumous)
Simon van der Meer (24 November 1925 – 4 March 2011)  Nobel Prize in Physics & accelerator physicists who discovered W and Z bosons
Baruch Samuel “Barry” Blumberg (July 28, 1925 – April 5, 2011)  Nobel Prize in Medicine (1976) for ‘discoveries concerning new mechanisms for the origin and dissemination of infectious diseases’ also identified the Hepatitis B virus, and later developed its diagnostic test and vaccine.
Willard Sterling Boyle (August 19, 1924 – May 7, 2011) co-inventor of the charge-coupled device and reciept of 2009 Nobel Prize in Physics for “the invention of an imaging semiconductor circuit—the CCD sensor”
Rosalyn Sussman Yalow (July 19, 1921 – May 30, 2011)  Co-winner of the 1977 Nobel Prize in Physiology or Medicine (together with Roger Guillemin and Andrew Schally) for development of the radioimmunoassay (RIA) technique.
Rudolf Ludwig Mössbauer (January 31, 1929 – September 14, 2011) A German physicist best known for his 1957 discovery of recoilless nuclear resonance fluorescence for which he was awarded the 1961 Nobel Prize in Physics.
Har Gobind Khorana also known as Hargobind Khorana (January 9, 1922 – November 9, 2011) A Indian-born American biochemist who shared the Nobel Prize in Physiology or Medicine in 1968 with Marshall W. Nirenberg and Robert W. Holley for research that helped to show how the nucleotides in nucleic acids, which carry the genetic code of the cell, control the cell’s synthesis of proteins.


Today I was reading the book titled “World of Physics Volume II by Jefferson Weaver”; a great book that contains Nobel speeches and information on some of the greatest contributions in science, but more on that later. Anyways back to the topics, in that book in the chapter regarding the Scattering Experiment by Lord Rutherford, in it he coined the terms as Alpha(α), Beta(β) and Gamma(γ). But in the paper he called them as Alpha, Beta and Gamma Rays. While I discarded it as irrelevant, in my further reading the terms used were as α and β particles while γ Rays. That was what burned my curiosity : Why α and β as particles while γ as rays?
Now when I looked up for definition of a particle I found this

“… a particle is a small localized object to which can be ascribed several physical properties such as volume or mass…” – Wikipedia

And the answer to question is the mass of the three elements.

Alpha (α) : Alpha particles are made of 2 protons and 2 neutrons.
This means that they have a charge of +2, and a mass of 4.

Beta (β) : Beta particles are made of 1 electron. Beta particles have a charge of minus 1, and a mass of about 1/2000.

Gamma (γ) : Gamma are not particle rather they are a bust of energy i.e. they are in wave form. Thus it has neither any charge nor any mass.

Hence Gamma as called rays while the other as particles.

Magic of Shadows

Well just today morning I was reading in the college library a basic book that was, if I am correct, a 11th grade physics book. The first topic was unsurprisingly about the ‘States of Matter’ and some student, in the past, had written in the margin a small but interesting question; which I admit I dismissed. But later in further reading the question came back to hunt me :)
Now back to the interesting question :

“Why do transparent objects, like glasses, have shadows?”

After dusting through various books i found this accurate description of shadow :

“Shadow, a dark area within or next to an illuminated one. Shadows are caused by the blocking of light by an object….”

Finally after almost 2 hrs I found the answer that is hopefully accurate :
In general, if any body or object is sheded with some light on it. It is observed that some of the light passes through the body, while others are reflected off it, the rest is absorbed by it. In the Transparent materials, the intensity of incident light passing through the body portion in most cases is much larger than the intensity of the reflected and absorbed, but this is highly dependent on the angle of incidence of light. Therefore, edges, curved parts of the incident light passing through the body portion varies from place to place. Hence the transparent bodies do allow light to pass but the shadow created is essentially of the wind and dust particles, which is seen as darker spots.
Do excuse any grammatical mistakes. And if there is any mistake please do comment. This is my first time of writing the blog and I intend to update it a frequently as possible with more such curious questions that arose in my mind.