
Teenager Finds Classical Alternative to Quantum Recommendation Algorithm - okket
https://www.quantamagazine.org/teenager-finds-classical-alternative-to-quantum-recommendation-algorithm-20180731/
======
vanderZwan
> _“Tang is killing [Kerenidis and Prakash’s] quantum speedup, but then in
> another sense Tang is giving a big improvement and building on what they
> did. Tang never would have come up with this classical algorithm but for
> their quantum algorithm,” Aaronson said._

I think this deserves more emphasis: regardless of whether or not we need a
quantum computer in the end, as a _model_ quantum computing is apparently
useful to do research with and advance the status quo of our knowledge.

~~~
akvadrako
This is a bit speculative, but I suspect quantum theory is essentially god's
programming language. It seems to crop up everywhere we look, like in
psychology, biology, machine learning, computer science and general
probability.

~~~
jonny_eh
> essentially god's programming language

That metaphor seems to confuse people more than it clarifies. Did you perhaps
mean "nature's programming language"?

~~~
kybernetikos
I think 'nature' would be confusing here, since we also use it for the
concrete, manifest nature. As used here, and in many other phrasings, and by
analogy with religon, 'god' is probably meant to be the principles and forces
underlying manifest nature.

~~~
akvadrako
And if nature was a programmer, I don’t see how that’s different from god.

~~~
qubex
In your paradigm ”nature” is what ”god” ”programmed” with his ”quantum
language”.

~~~
akvadrako
Not really. I think nature = universe = god. Again, a bit speculative.

~~~
PinkMilkshake
Deepak Chopra, is that you?

~~~
jonnybgood
More like Baruch Spinoza:

[https://en.wikipedia.org/wiki/Baruch_Spinoza](https://en.wikipedia.org/wiki/Baruch_Spinoza)

~~~
andai
Jews _hate_ him!

------
proto-n
I just want to mention that the "recommendation systems" angle is quite
unimportant here. This is a result in complexity theory, a resolution of the
question "whether you actually need a quantum computer to sample the rows of a
partially-specified low-rank matrix in polylogarithmic time" (as Scott
Aaronson puts it [1]).

While this problem does occur in matrix factorization based recommenders,
there are a lot of solutions for it without quantum computers that perform
well, and it's far from being _the one method_ for recommendation.

[1]
[https://www.scottaaronson.com/blog/?p=3880](https://www.scottaaronson.com/blog/?p=3880)

~~~
vanderZwan
> _" whether you actually need a quantum computer to sample the rows of a
> partially-specified low-rank matrix in polylogarithmic time"_

Could that be used in clustering algorithms in BioInformatics?

EDIT: Sorry, Aaronson's writing is just too funny not to put that quote in
full context:

> _On the Hacker News thread, some commenters are lamenting that such a
> brilliant mind as Ewin’s would spend its time figuring out how to entice
> consumers to buy even more products that they don’t need. I confess that
> that’s an angle that hadn’t even occurred to me: I simply thought that it
> was a beautiful question whether you actually need a quantum computer to
> sample the rows of a partially-specified low-rank matrix in polylogarithmic
> time, and if the application to recommendation systems helped to motivate
> that question, then so much the better. Now, though, I feel compelled to
> point out that, in addition to the potentially lucrative application to
> Amazon and Netflix, research on low-rank matrix sampling algorithms might
> someday find many other, more economically worthless applications as well._

~~~
jtbayly
"research on low-rank matrix sampling algorithms might someday find many
other, more economically worthless applications as well."

I'm not sure whether this is a typo, and he means to say that there might be
more economically worthwhile applications, or whether he's trolling the people
complaining that this is useless by pointing out that there are real economic
benefits to it _right now._

~~~
btilly
Neither.

He's trolling the people who regret that the result of this research is
manipulating people. By pointing out that there is a real potential for
applications that they object to less.

~~~
rcoveson
It's a very broad definition of "manipulating people" that includes
recommendation algorithms. The problem, as stated, seems to call for an
implementation of a perfectly benign strategy for recommending content.

Clustering users by their ratings of various titles is the kind of thing any
hobbyist statistician might do to help their friends find movies they like
using online data sets.

There are methods to use data to improve people's experiences, and sometimes
corporations employ those methods.

~~~
dwaltrip
You must admit that there is a very large difference between a friend doing
something for me and a corporation doing the same thing.

~~~
tangentspace
What is the difference?

~~~
dwaltrip
A friend actually cares about you, your best interests, and long-term well-
being.

One's relationship with a corporation is very different. They don't know you
or necessarily care very much about your long term interests.

------
FactolSarin
Sometimes I think I'm smart because I can configure WebPack, and then I read
an article like this.

~~~
efdee
I'd like to see him try that.

~~~
travmatt
Can he vertically center a div though?

~~~
Aeolun
Flex!

~~~
mkoryak
tables!

~~~
i6mi6
Early 2000s strike back

------
devy
A little bit backdrop of Ewin Tang: [http://www.uta.edu/utamagazine/archive-
issues/2010-13/2012/1...](http://www.uta.edu/utamagazine/archive-
issues/2010-13/2012/12/cultivating-genius/index.html)

~~~
fatjokes
I like the last line:

> And what about the future of UT Arlington’s latest wunderkind, Ewin Tang? “I
> haven’t come up with anything that is really ingenious yet,” he says. Be
> patient; he’s only 12.

It only took 6 years. Not bad at all!

~~~
theparanoid
As someone who finished undergrad classes as a teenager. I totally failed to
live up to my potential.

~~~
contingencies
Don't sell yourself short. Lots of important stuff happens when inquiring
minds age and have the benefit of cross-disciplinary experience and
perspective, plus new social, temporal and fiscal resources.

------
cwkoss
Scott Aaronson posted about this on his blog

[https://www.scottaaronson.com/blog/?p=3880](https://www.scottaaronson.com/blog/?p=3880)

I like his update - a message to Hacker News commenters:

"On the Hacker News thread, some commenters are lamenting that such a
brilliant mind as Ewin’s would spend its time figuring out how to entice
consumers to buy even more products that they don’t need. I confess that
that’s an angle that hadn’t even occurred to me: I simply thought that it was
a beautiful question whether you actually need a quantum computer to sample
the rows of a partially-specified low-rank matrix in polylogarithmic time, and
if the application to recommendation systems helped to motivate that question,
then so much the better. Now, though, I feel compelled to point out that, in
addition to the potentially lucrative application to Amazon and Netflix,
research on low-rank matrix sampling algorithms might someday find many other,
more economically worthless applications as well."

~~~
tensor
That seems a bit passive aggressive. I don't think economical value is what is
in question, but rather the social impact of the application (or lack of
positive social impact).

Applications can be both economically valuable _and_ have positive social
impact. Now recommender systems are in fact useful to discover new things, not
just to entice people to buy more. E.g. finding new music, related research,
or other things.

~~~
jholloway7
The tone of his comment seems to me he's just frustrated a community of
programmers took the conversation down the path of debating the merits of
recommendation systems rather than exploring the more general applicability of
the algorithm in other problem spaces.

~~~
wilg
I agree with him. Half the time you'll enter an HN discussion and the most
upvoted comment will an unrelated bikeshedding discussion.

Usually one of these:

\- "I love the idea but can we talk about how the website doesn't look good
when CSS is disabled?"

\- "25MB of JavaScript? Really? You know, websites used to..."

\- "This website is impossible to read because the contrast ratio is too low
and I am personally offended."

\- "Did anyone else get an ad from this news website? Why does advertising
exist?"

\- "An obscure open source project uses the same name as this unrelated
business. Have you no shame?"

\- "The website looks weird on mobile, by which I mean my rooted Android phone
running Opera."

\- "The text is too big."

\- "The text is too small."

~~~
MadcapJake
When did "comment" transition into "thought-provoking well-defended essay"? Is
there no water cooler talk on the internet anymore? I find interesting tidbits
and interesting tangents here on HN and I appreciate it all!

~~~
Asquil
I think the "most upvoted comment" part is important here. Tangents are indeed
good to have, but I don't think they should occupy the most visible parts of
the comment section.

------
jaddood
From the paper,

> The only difference between Theorem 1 and its quantum equivalent in [13] is
> that the quantum algorithm has no ε approximation factors (so ε=0 and 1/ε
> does not appear in the runtime). Thus, we can say that our algorithm
> performs just as well, up to polynomial slowdown and ε approximation
> factors.

With ε being the accepted margin of error, theorem 1 being the algorithm
produced by Tang, and [13] being a reference to Kerenidis and Prakash's
quantum algorithm kept here in the quote for fidelity of quoting.

This means that this algorithm is not really a substitue for the quantum
algorithm because it will require a level of error to be accepted (something
which might work in recommendation engines, but not necessarily outside that
context) and it still has polynomial slowdown over the quantum algorithm. One
thing to note is that not all quantum algorithms will perform exponenttially
better than their classical counterparts. Particularily, some quantum search
algorithms perform only quadratically better than the classical search
algorithms. This means that even if an exponential speedup was not achieved by
quantum computers, (which it still is because of the ε factor meaning they
don't give the same results) it is expected that they still achieve polynomial
speedup as they do in this case.

In conclusion, stating that this algorithm threatens the prospects of quantum
computation is probably an exageration.

------
charleslmunger
Scott Aaronson wrote about this on his own blog too:
[https://www.scottaaronson.com/blog/?p=3880](https://www.scottaaronson.com/blog/?p=3880)

------
rukittenme
Wow good on this guy. I thought it might have been a high-school student
reading the title but he's a PHD candidate. Incredible. What an accomplishment
at 18 to be lecturing a room of PHD holders.

~~~
gwern
It is, but not as rare as you might think! I've been reading some of the old
books/papers about SMPY from the 1970s, a talent search study which uses the
SAT-M to screen for visuospatially-gifted middle schoolers; they then study
them and try to accelerate their education with summer camps, advanced math
classes, and grade-skipping and/or early enrollment in Johns Hopkins (where
SMPY is based). SMPY was a big part of making acceleration for gifted children
acceptable in America, when the conventional wisdom was that they should be
forced into regular classes for their own good.

What they often did early on was, around age 14, SMPYers would be admitted to
Johns Hopkins to typically start taking math and computer science courses, at
which they would often excel and be at the top of the class, expected to go on
to post-graduate work around 19, and fit in so well that fellow students and
their teachers often (when surveyed or asked) didn't realize they were so
young. If you look in OP, that describes Tang remarkably well.

~~~
paulpauper
_post-graduate work around 19_

depends on the subject. Did computer science exist as a course in the 70's?

~~~
gwern
It certainly did, as that is what many of the kids were enrolled in...

------
nsxwolf
Skipped 4th through 6th grades. Impressive. Is this innate or did his parents
do something to make this happen? Is there anything I'm supposed to be doing
with my own kids? How/when do you know when your child has this potential?

~~~
acangiano
Nature is important but people massively underestimate the nurturing
component. Parents are most definitely key for these types of outcomes. If
you're not familiar with the story already, read about the Polgar sisters.
[https://www.psychologytoday.com/us/articles/200507/the-
grand...](https://www.psychologytoday.com/us/articles/200507/the-grandmaster-
experiment)

To your question, my immediate answer was, "let them play outside". But it
sounds dismissive of what you are asking. So the better answer is: provide
them with the opportunity to learn, encourage their curiosity, praise them for
their work not innate intelligence while still telling them that they are
smart, create an environment that values and promotes education, create a
program for them to follow when they show interest in a particular discipline,
have great mentors help them develop, etc.

The truth is, there is always going to be a compromise between having a care-
free childhood and top performance from an early age. You can't really have
both no matter how smart your kids are. Asian parents stereotypically tend to
opt for the latter end of the spectrum with, on average, very successful
outcomes.

~~~
paulpauper
imho, I think ppl actually overestimate the role of parenting. Often extremely
gifted children (as Tang and Tao are/were) will have their interests piqued by
something, and then on their own volition learn everything they can about it.
There isn't much prodding by the parents. For someone with an IQ of 140+,
maybe doing calculus problems is more fun than video games.

~~~
l9k
The interest must come from the kid, but there are conditions that enable this
interest. From a previously mentioned link in this thread [1], Tang's father
is a bioengineer professor, which means:

1\. Financial stability in the family, and it seems that both parents where
emotionaly supportive

2\. The father is knowledgeable in sciences, that means he can orient the
learning and use his network

3\. The father let his son work in his nanotechnology lab

[1] [http://www.uta.edu/utamagazine/archive-
issues/2010-13/2012/1...](http://www.uta.edu/utamagazine/archive-
issues/2010-13/2012/12/cultivating-genius/index.html)

------
JackFr
I wish an editor would step in:

(1) limit the use of 'exponentially faster', simply for the grating
repetition. The phrase is used 5 times in the article.

(2) In an article that is about time complexity of algorithms, be precise
about terms like 'exponentially faster'.

(3) In an article that is about quantum computing, don't use 'quantum' in its
colloquial sense of 'significant'. That is 'quantum' in quantum computing is
different than quantum in 'quantum increase'. The latter is a suspect usage,
but potentially defensible as colloquial; mixing the two in the same paragraph
reads poorly.

~~~
jessriedel
Where does it say "quantum increase" in the article? "Quantum speedup" does
appear, but this has a specific technical meaning and it is not being used in
the colloquial sense. It means that there is an efficient quantum algorithm
for solving the computational task but no efficient classical one.

~~~
HelloNurse
I consider this the colloquial sense: the speedup (or, more generically, the
"increase" of throughput, quality, or other performance indicators) obtained
by using quantum computers.

Unlike the irreducibly mathematical and very narrow concept of "exponential
increase", which could be plausibly misunderstood, a quantum speedup (or
increase) can be correctly abstracted to the trivial pattern of _doing things
in a different way which performs better_ , without really needing to
understand the problem and the solution; it's very surprising to hear the term
misused to mean "really big". How could it happen?

------
classichasclass
I think this might represent an example of another unique value of quantum
computing: as a way to get us thinking about computing problems via a
different paradigm that can perhaps be translated back to classical computing.

------
jack6e
This is awesome work, and kudos to Tang, but I am also really impressed with
how his advisor, Scott Aaronson, seems to have so selflessly supported his
research and given him full credit. Even in Aaronson's quotes within the
article he talks about it entirely as Tang's work, and he seems to have
considered Tang's best interests in deciding how and when to let him present
the work - even that he let Tang present it!

Given a different person, we may have read about "UT-Austin Professor and
Quantum Researcher Finds Classical Alternative to Quantum Recommendation
Algorithm" (with generic help from students in a footnote somewhere). It's
great to see this type of collegial mentorship.

~~~
lisper
Scott Aaronson is just one of the most awesome human beings ever. He is
brilliant yet modest, and his writing is at once deeply enlightening and
eminently accessible. The world would be a better place if more academics
adopted him as a role model.

~~~
cambalache
Just to provide a counterpoint based on the scant evidence of his blog (post
and comments). He is , of course , brilliant, and has a refreshing no-nonsense
approach. Modest, he is not, not that is anything wrong with that, I would
call modest for example Terence Tao a far more accomplished academic. This is
something that should be a "law", the more accomplished a person is the most
it can "afford" to be modest. So for example Einstein was more modest than say
Feynman, and Edward Witten is way way more modest than your typical string
theorist.

The other thing I dont like about Aaronson is his weird fetish with STEM
people , he seems to think scientists and technologists are somehow superior
or more worthy than regular folk. I also dont agree with some of his opinions
on the actions of the state of Israel, but I will avoid that, being this the
Internet.

~~~
jessriedel
I've never known Scott to be anything but unfailingly modest, both in person
and on his blog. What specifically are you referring to?

~~~
lostlogin
I had a look and the first thing I found was him calling for an academic
boycott against New Zealand - presumably for NZs support of the UN resolution
against Israel’s Palestinian settlements. This is an interesting approach to
dealing with criticism.

[https://www.scottaaronson.com/blog/?p=247](https://www.scottaaronson.com/blog/?p=247)

~~~
edanm
I think you're misunderstanding the post. It's a satire of similar such blog
posts which are calling for the boycott of Israel. It's trying to (humorously)
make the case that boycotting Israel makes about as much sense as boycotting
New Zealand for their treatment of the native population, or likewise
boycotting China over Tibet, etc, etc.

------
dvh
Conjecture: for every quantum algorithm that is faster than current classical
algorithm exists yet undiscovered classical algorithm that is equally fast.

~~~
qzw
Not sure if you’re being serious, but there are already quantum algorithms
that have been mathematically proven to not be dequantizable, i.e. have no
possible classical version that's as fast.

~~~
Ar-Curunir
What's your definition of "as fast"? We can't separate BQP from P right now.
That is, we don't know any problems that run in polynomial time on a quantum
computer, but provably have no polynomial time classical algorithms.

~~~
qzw
“As fast” in the big-O sense. Here’s what Scott Aaronson says in reply to one
of the comments on his blogpost about this paper:

 _I should point out, though, that in many cases (Simon’s problem, period-
finding, Forrelation, quantum walk on glued trees…), people have proved
exponential separations between the quantum and randomized query complexities,
which means that there certainly won’t be a dequantization in those cases
along the same lines as what Ewin did._

------
tsucres
The paper [1] states:

> There is a classical algorithm whose output distribution is O(ε)-close in
> total variation distance to the distribution given by l2-norm sampling from
> the ith row of a low- rank approximation D of A in query and time complexity
> [O(poly-func)] where δ is the probability of failure.

So the classical algorithm would give a "sufficiently close" approximation of
what the QML would output? The article doesn't mention this at all. Is it fair
to compare a quantum algorithm with an equivalent classical _approximation_
algorithm?

From the quanta magazine article:

> Computer scientists had considered [the recommendation problem] to be one of
> the best examples of a problem that’s exponentially faster to solve on
> quantum computers — making it an important validation of the power of these
> futuristic machines. Now Tang has stripped that validation away.

Has he really?

[1]
[https://arxiv.org/pdf/1807.04271.pdf](https://arxiv.org/pdf/1807.04271.pdf)

~~~
sheroze
> As a consequence, we show that Kerenidis and Prakash’s quantum machine
> learning (QML) algorithm, one of the strongest candidates for provably
> exponential speedups in QML, does not, in fact, give an exponential speedup
> over classical algorithms.

The comparison is fair and the author is giving a metric to compare the
algorithms too.

------
TheRealPomax
But why does the title focus on the person's age, instead of their skill? This
should just read "Grad student finds classical alternative to quantum
recommendation algorithm". Sure, he's young, but that's also 100% irrelevant
to the actual work presented.

~~~
Doradus
His youth is remarkable, so they remarked on it. I'm not sure what about this
troubles you.

~~~
TheRealPomax
Given the audience of the magazine in question, writing the headline to focus
on how young he is (which tells us nothing in relation to quantum computing)
instead of the fact that this is a grad student (which DOES tell us something:
it gives readers a frame of reference in terms of this person's academic
knowledge and skillsets) is disappointing at best, and clickbait at worst.

------
Elrac
I would have liked to read this article, but the page refuses to load in my
bog-standard Mozilla browser.

Ironically, there's an article in HN today about "The Bullshit Web." This is
exactly what that article is about. Apparently Quanta Magazine is trying to do
something clever, and that "clever" thing is stopping their content from
reaching me.

~~~
suluke
Since I really had trouble finding a way to read the article (source seems to
have depublished it?) I just wanted to leave a small how-to on how I succeeded
eventually:

    
    
      - Look up the page in wayback machine
      - Open the first snapshot
      - JS seems to delete the content immediately
      - Open developer tools
      - Reload the page
      - View the HTML response in the response preview window
    

Bullshit Web it is

 _Edit: Article seems to be back online now_

------
pulkitsh1234
And here I am, struggling to solve TopCoder problems....

~~~
pseudolus
You can always console yourself with the knowledge that you* can rent a car
and buy a beer in any state and he can't.

*I'm assuming you're at least 26.

~~~
DoctorOetker
... and listen MC++ all night long

------
rurban
I don't get why they don't just prepare the dataset for optimal search
beforehand, as done in compgeom, like a quadtree or voronoi or in this case
clustering into k regions. K dimensions are not so hard to handle. Then search
will always be logarithmic. Even Google prepares it's datastructures for fast
queries, a reverse index.

------
peter_retief
I am impressed, what an interesting piece

------
carbocation
Has anyone started an implementation of this yet in python, go, rust, etc?

~~~
DoctorOetker
From the paper:

"Second, while the recommendation system algorithm we give is asymptotically
exponentially faster than previous algorithms, there are several aspects of
this algorithm that make direct application infeasible in practice. First, the
model assumptions are somewhat constrictive. It is unclear whether the
algorithm still performs well when such assumptions are not satisfied. Second,
the exponents and constant factors are large (mostly as a result of using
Frieze, Kannan, and Vempala’s algorithm [10]). We believe that the “true”
exponents are much smaller, but our technique is fairly roundabout and likely
compounds exponents unnecessarily. These issues could be addressed with more
straightforward analysis combined with more sophisticated techniques."

------
newyearnewyou
Can anyone explain the significance of this in a few sentences for the non-
expert? I read the article but am struggling to understand.

------
hi41
This is amazing and he is just 18 years old!

------
kbatdorf
Maybe now Netflix will show me titles I'm actually interested in.

~~~
the_new_guy_29
Not enough content on netflix unfortunetly

------
sharpneli
The headline makes my eye twitch. It is technically correct but pushes age bit
too much into forefront. It is a bachelor thesis work supervized by Scott
Aaronson of all people.

It is going to be really interesting to see if there are other algorithms
where we find classical algorithms that run in polynomial time.

~~~
dljsjr
Maybe I'm just easily impressed but the idea of a 17 year old who skipped
three grades and is already a third-year university student who was talented
enough to catch Scott's attention and then address a technically challenging
problem like this certainly warrants at least some recognition for the age at
which he made this accomplishment.

Or maybe I'm just not smart enough to hang out on Hacker News.

~~~
archgoon
The issue is that the title actually diminishes the accomplishment by focusing
on the wrong thing. The work is impressive independent of the authors age. By
emphasizing the age, the focus shifts from what he did, which he should be
proud of, to something he will no longer have in two years.

~~~
n4r9
As someone who has done research in quantum information, the age shifts this
result from "very impressive" to "extremely impressive".

------
estomagordo
When I was 18, I could operate an oven.

------
known
50% of land is uninhabited

------
zghst
Poor Chad Rigetti

------
dingoegret
Chinese geniuses have done it again

------
greg7mdp
If he had discovered this algo a few years back, he might have won the $1
million netflix prize
([https://en.wikipedia.org/wiki/Netflix_Prize](https://en.wikipedia.org/wiki/Netflix_Prize)).

~~~
dapf73
I'm pretty sure Netflix can give him another million.

~~~
fatjokes
Pretty sure at the current rate star ML researchers are paid, a million for
Tang would be low-balling him.

~~~
quickthrower2
It could just be a handcuffless gift.

