Skip to content
By using Twitter’s services you agree to our Cookies Use. We and our partners operate globally and use cookies, including for analytics, personalisation, and ads.
  • Home Home Home, current page.
  • About

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @
  • Language: English
    • Bahasa Indonesia
    • Bahasa Melayu
    • Català
    • Čeština
    • Dansk
    • Deutsch
    • English UK
    • Español
    • Filipino
    • Français
    • Hrvatski
    • Italiano
    • Magyar
    • Nederlands
    • Norsk
    • Polski
    • Português
    • Română
    • Slovenčina
    • Suomi
    • Svenska
    • Tiếng Việt
    • Türkçe
    • Ελληνικά
    • Български език
    • Русский
    • Српски
    • Українська мова
    • עִבְרִית
    • العربية
    • فارسی
    • मराठी
    • हिन्दी
    • বাংলা
    • ગુજરાતી
    • தமிழ்
    • ಕನ್ನಡ
    • ภาษาไทย
    • 한국어
    • 日本語
    • 简体中文
    • 繁體中文
  • Have an account? Log in
    Have an account?
    · Forgot password?

    New to Twitter?
    Sign up
michael_nielsen's profile
michael_nielsen
michael_nielsen
michael_nielsen
@michael_nielsen

Tweets

michael_nielsen

@michael_nielsen

Searching for the numinous. Co-purveyor of https://quantum.country/ 

San Francisco, CA
michaelnielsen.org
Joined July 2008

Tweets

  • © 2019 Twitter
  • About
  • Help Center
  • Terms
  • Privacy policy
  • Imprint
  • Cookies
  • Ads info
Dismiss
Previous
Next

Go to a person's profile

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @

Promote this Tweet

Block

  • Tweet with a location

    You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more

    Your lists

    Create a new list


    Under 100 characters, optional

    Privacy

    Copy link to Tweet

    Embed this Tweet

    Embed this Video

    Add this Tweet to your website by copying the code below. Learn more

    Add this video to your website by copying the code below. Learn more

    Hmm, there was a problem reaching the server.

    By embedding Twitter content in your website or app, you are agreeing to the Twitter Developer Agreement and Developer Policy.

    Preview

    Why you're seeing this ad

    Log in to Twitter

    · Forgot password?
    Don't have an account? Sign up »

    Sign up for Twitter

    Not on Twitter? Sign up, tune into the things you care about, and get updates as they happen.

    Sign up
    Have an account? Log in »

    Two-way (sending and receiving) short codes:

    Country Code For customers of
    United States 40404 (any)
    Canada 21212 (any)
    United Kingdom 86444 Vodafone, Orange, 3, O2
    Brazil 40404 Nextel, TIM
    Haiti 40404 Digicel, Voila
    Ireland 51210 Vodafone, O2
    India 53000 Bharti Airtel, Videocon, Reliance
    Indonesia 89887 AXIS, 3, Telkomsel, Indosat, XL Axiata
    Italy 4880804 Wind
    3424486444 Vodafone
    » See SMS short codes for other countries

    Confirmation

     

    Welcome home!

    This timeline is where you’ll spend most of your time, getting instant updates about what matters to you.

    Tweets not working for you?

    Hover over the profile pic and click the Following button to unfollow any account.

    Say a lot with a little

    When you see a Tweet you love, tap the heart — it lets the person who wrote it know you shared the love.

    Spread the word

    The fastest way to share someone else’s Tweet with your followers is with a Retweet. Tap the icon to send it instantly.

    Join the conversation

    Add your thoughts about any Tweet with a Reply. Find a topic you’re passionate about, and jump right in.

    Learn the latest

    Get instant insight into what people are talking about now.

    Get more of what you love

    Follow more accounts to get instant updates about topics you care about.

    Find what's happening

    See the latest conversations about any topic instantly.

    Never miss a Moment

    Catch up instantly on the best stories happening as they unfold.

    1. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      Had some fun this afternoon re-analyzing the circuit for quantum teleportation. Here's a proof I found that the circuit works. The circuit to be verified: top two qubits are Alice's, including the state psi to be teleported. Bottom qubit is Bob's - want to show it outputs psi.pic.twitter.com/w7Bl3FPZ1B

      4 replies 50 retweets 226 likes
      Show this thread
    2. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      The shared state (|00>+|11>)/sqrt 2 is symmetric, so the original circuit is equivalent to one where we move the CNOT target to the third qubit:pic.twitter.com/Dnn9AzBvN8

      2 replies 0 retweets 9 likes
      Show this thread
    3. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      We can measure the second qubit as early as we like, without changing the output from the circuit. In fact, we can do the measurement right at the beginning of the protocol, giving:pic.twitter.com/obUVj5snWf

      2 replies 0 retweets 12 likes
      Show this thread
    4. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      We can now ignore the second qubit - it no longer has any impact on the output we're interested in. We can also commute the X^x past the CNOT target, to get:pic.twitter.com/AqM7vyjC48

      2 replies 0 retweets 12 likes
      Show this thread
    5. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      I don't know of any way of computing the output here, except to do the algebra:pic.twitter.com/KQ4FnQgP0C

      1 reply 0 retweets 10 likes
      Show this thread
    6. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      Of course, we could have just done the algebra for the whole 3-qubit system up front. It's really not very complicated, & that's how I've always done it in the past. But I noticed this approach a few hours ago, & rather like it. It's in some sense longer, but more elegant.

      1 reply 0 retweets 11 likes
      Show this thread
    7. michael_nielsen‏ @michael_nielsen May 23
      • Report Tweet

      No claim that this is new! But it was new & pleasing to me, a slightly new way of seeing an old friend.

      4 replies 0 retweets 28 likes
      Show this thread
      michael_nielsen‏ @michael_nielsen May 24
      • Report Tweet

      Update: In fact, it is possible to analyze the two-qubit circuit with almost no algebra. Ignoring the final Z^z gate, the main thing to analyze is this circuit:pic.twitter.com/WcJOsjJCrN

      10:21 AM - 24 May 2019
      • 6 Likes
      • Zachary Larson 🎙Papa Tango🎙 Dan Zimmerman Paul Secular 🇪🇺 🌻 horses Sebastian Bensusan
      2 replies 0 retweets 6 likes
        1. New conversation
        2. michael_nielsen‏ @michael_nielsen May 24
          • Report Tweet

          We run the state through the CNOT, and then Hadamard + measurement is equivalent to measuring in the <+| or <-| basis:pic.twitter.com/oWK4nI63El

          1 reply 0 retweets 4 likes
          Show this thread
        3. michael_nielsen‏ @michael_nielsen May 24
          • Report Tweet

          The resulting conditional states are as shown, and we can simply cancel the Z^z term:pic.twitter.com/Pvuyw9FSVQ

          2 replies 0 retweets 7 likes
          Show this thread
        4. michael_nielsen‏ @michael_nielsen May 24
          • Report Tweet

          I really like the first part of the proof: it's just a quantum one-time pad. I don't quite know how to think about the second part of the proof. Why does measuring in the |+>, |-> basis work? It's easy to prove it does, but I don't have a really good explanation for why.

          2 replies 0 retweets 6 likes
          Show this thread
        5. End of conversation
        1. New conversation
        2. Joe Fitzsimons‏ @jfitzsimons May 26
          • Report Tweet
          Replying to @michael_nielsen

          You can reach this by pulling the Z^z back through the CNOT to get Z^z on qubits 1 and 2, and since Z^z on the qubit 2 now acts on |0>, it can be removed. The Z^z on qubit 1 can be pulled back through the CNOT and Hadamard, then the measurement output is always |0>.

          1 reply 0 retweets 1 like
        3. 1 more reply

      Loading seems to be taking a while.

      Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.

        Promoted Tweet

        false

        • © 2019 Twitter
        • About
        • Help Center
        • Terms
        • Privacy policy
        • Imprint
        • Cookies
        • Ads info