aspuru-list November 2018

aspuru-list@lists.fas.harvard.edu

8 participants
20 discussions

[Aspuru-Guzik Group List] Group meeting, Fri Nov 16, 10 AM

by Ian Kivlichan

Hi all, We'll have group meeting tomorrow (Friday) morning at 10 AM, with talks from Xiao Yuan and Sam McArdle from Oxford. We'll be in Davenport East in Toronto and the Division Room at Harvard. See below for titles and abstracts :) All the best, Ian ----------------- Title: Variational quantum simulation of imaginary time evolution Speaker: Xiao Yuan Imaginary time evolution is a powerful tool for studying quantum systems. While it is simple to simulate with a classical computer, the time and memory requirements scale exponentially with the system size. Conversely, quantum computers can efficiently simulate quantum systems, but not non-unitary imaginary time evolution. We propose a hybrid, variational algorithm for simulating imaginary time evolution on a quantum computer. We use this algorithm to find the ground state energy of many-particle systems; specifically molecular Hydrogen and Lithium Hydride, finding the ground state with high probability. Our method can also be applied to general optimisation problems and quantum machine learning. As our algorithm is hybrid, suitable for error mitigation, and can exploit shallow quantum circuits, it can be implemented with current quantum computers. Title: Error mitigation and quantum chemistry Speaker: Sam McArdle Variational algorithms may enable classically intractable simulations on near-future quantum computers. However, their potential is limited by hardware errors. It is therefore crucial to develop efficient ways to mitigate these errors. Here, we propose a stabiliser-based method which enables the detection of up to 60 - 80 % of depolarising errors. Our method can easily be implemented on current quantum hardware. Numerical simulations show that our method can significantly increase the accuracy of noisy calculations, especially when combined with existing error mitigation techniques.

5 years, 5 months

[Aspuru-Guzik Group List] [qip] John Napp talk today at 1:30pm in 6-310

by Aram Harrow

Dear quanta, I mentioned this talk earlier - now it has a room: 6-310. Here are some more details. speaker: John Napp title: Low-depth gradient measurements can improve convergence in variational hybrid quantum-classical algorithms abstract: Variational algorithms, a broad class of quantum algorithms, have been proposed in the context of quantum simulation, machine learning, and combinatorial optimization as a way of potentially achieving a quantum speedup on a near-term quantum device for a computational problem of practical interest. Such algorithms use the quantum device only to prepare parameterized quantum states and make simple measurements. A classical "outer loop" uses the measurement results to perform an optimization of a classical function induced by a quantum observable which defines the problem. While most prior works have considered optimization strategies based on estimating the objective function and doing a derivative-free- or finite-difference-based optimization, a few have proposed directly measuring the gradient of the objective function. The measurement procedure needed requires coherence time barely longer than needed to prepare a trial state, and is much cheaper than procedures based on phase estimation. We prove that strategies based on such gradient measurements can admit substantially faster rates of convergence to the optimum in some contexts. We first define a natural black-box setting for variational algorithms which we prove our results with respect to. We define a simple but natural class of problems for which a variational algorithm based on gradient measurements and stochastic gradient descent converges to the optimum quadratically faster in the precision than any possible strategy based on estimating the objective function itself. We also present general upper bounds for the cost of variational optimization for derivative-free, stochastic gradient descent, and stochastic mirror descent methods in a convex region. -aram _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

5 years, 5 months

[Aspuru-Guzik Group List] Important paper

by Alan Aspuru-Guzik

That we discussed at joint group meeting https://chemrxiv.org/articles/The_CryoEM_Method_MicroED_as_a_Powerful_Tool_… Apparently already published in ACS Cent Sci Best Alan -- Alán Aspuru-Guzik Professor of Chemistry and Computer Science | Vector Institute Canada 150 Research Chair in Quantum Chemistry | CIFAR Senior Fellow University of Toronto | 80 St George St | Toronto, ON M5S 3H6, Canada http://matter.toronto.edu Twitter @A_Aspuru_Guzik aspuru(a)utoronto.ca

5 years, 5 months

[Aspuru-Guzik Group List] Group meeting, Wed Nov 07, 11 AM

by Ian Kivlichan

Hi all, We'll have this week's group meeting tomorrow at 11 AM, with Cyrille Lavigne's talk. All the best, Ian

5 years, 5 months

[Aspuru-Guzik Group List] [qip] talk tomorrow at 11am

by Aram Harrow

Dear quanta, We will have a talk tomorrow at 11am by David Ding from Stanford in room 6-310. Title: A Quantum Multiparty Packing Lemma and the Relay Channel Abstract: Encoding classical information into a quantum system is one of the most fundamental questions of quantum information theory. Classic results in this area include the Holevo bound and the Holevo-Schumacher-Westmoreland theorem. The setup can be imagined as a black box which takes a random variable encoding the information as input and outputs a quantum state. Under appropriate conditions, the information can be retrieved via a decoding quantum measurement. In this work, we prove that decoders for different black boxes can be combined into one simultaneous decoder for a black box that takes as input the joint random variable across all the black boxes. This resolves a long-standing open problem in quantum network information theory known as simultaneous decoding and was made possible by Pranab Sen's recent quantum joint typicality lemma. We demonstrate the use of our results for the quantum relay channel, a possible communication model for quantum repeaters. _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

5 years, 5 months

[Aspuru-Guzik Group List] [Instructions] Siria is gone; who does what?

by Siria Serrano

Dear Group, Here are some general instructions to help you round out basic tasks in the coming weeks. *Calendars (Group, Events and Travel)*: Flo will manage the Group's calendars email or Slack him your requests for access. *Letters*: Email all links and requests for letters to aspuru.staff(a)gmail.com *Group Listserve: * Email all requests for access to aspuru.staff(a)gmail.com *HIO Matters*: Email a short note to the aspuru.staff(a)gmail.com account with any HIO, matters. A Harvard Lab Administrator will follow up with further directions. *Mail: *Tim will check mail, bring it down to the coat closet and email you if you have mail. *Slack*: Hannah, Si Yue and Tony will manage Slack and are able to invite new members, email any of them your request for access. *Travel Logistics (airfare, hotel, etc) and Reimbursements*: Harvard based group members are instructed to email a short note to the aspuru.staff(a)gmail.com account with the name of the event, or conference, location, dates and all receipts. A Harvard Lab Administrator will follow up with further directions. Toronto based group members will see no change, Shanna and the new Assistant starting tomorrow, Maria Zuniga will process all of your reimbursements. Shanna will email the group Maria's email once she has one. *Terminations:* If there are any changes to your move to Toronto date or appointment end date email a short note to the aspuru.staff(a)gmail.com account with the change and date when it will occur. A Harvard Lab Administrator will follow up with further directions. *CCB is in the process of naming a new Lab Admin to support the group and we will email everyone their name and contact information as soon as it is available. Until then, please follow these instructions.* Very best regards, Siria -- *Siria Serrano* *Laboratory Administrator* *Aspuru-Guzik Group* *Harvard University **Department of Chemistry and Chemical Biology* *12 Oxford St. M 136* *Cambridge, MA 02138* *P:** (617) 496-1716 <%28617%29%20496-1716>** F: **617-496-9411 <617-496-9411>*

5 years, 5 months

[Aspuru-Guzik Group List] Joint Quantum Seminar - Wednesday, November 7, 2018 @ 4:00 - Prof. Rob Schoelkopf

by Dakoulas, Samantha R

Joint Quantum Seminar Wednesday, November 7, 2018 4:00 PM, Jefferson 250 Prof. Rob Schoelkopf, Yale University “The Prospects for Scalable Quantum Computing with Superconducting Circuits”” Dramatic progress has been made in the last decade and a half towards realizing solid-state systems for quantum information processing with superconducting quantum circuits. Artificial atoms (or qubits) based on Josephson junctions have improved their coherence times more than a million-fold, have been entangled, and used to perform simple quantum algorithms. The next challenge for the field is demonstrating quantum error correction that actually improves the lifetimes, a necessary step for building more complex systems. At Yale we have been pursuing a hardware-efficient approach for error correction, that relies on encoding information in a superconducting cavity, the so-called “cat codes.” With this approach, we have applied real-time measurements and feedback to achieve the first extension of the lifetime of a quantum bit through error correction. For scaling, an attractive approach is the modular architecture, in which small quantum processors are networked together using microwave signals on superconducting transmission lines. I will present the first implementation of a teleported C-NOT gate, which is a key building block for the modular approach. Student Presentation (Mian Zhang) at 4:00 Guest Presentation at 4:30 Refreshments will be provided Samantha Dakoulas Faculty Assistant to Professors Lukin & Greiner & their groups Department of Physics 17 Oxford St., Lyman 324A Cambridge, MA 02138 P. (617) 496-2544

5 years, 6 months

[Aspuru-Guzik Group List] Special ITAMP lunch seminar - Marina Litinskaya, UBC (November 6th)

by Zolfaghari Jooya, Hossein

*Speaker: *Marina Litinskaya (University of British Columbia) *Date:* Tuesday, November 6th *Time:* 12:00-1:00 pm Includes Pizza. *Title: * Negative refraction in atomic gases *Abstract: *Negative refraction of light is a fascinating phenomenon, since recently available in artificial solids, but not yet achieved in gases. I will show that negative refraction can be realized in a periodically modulated cold atomic gas, in the setup similar to the scheme developed for photonic crystals. However, the intuition coming from photonic crystal optics encounters two challenges: poorly defined gas boundary and weak gas-light coupling combined with strong resonant absorption. Nonetheless, our calculations demonstrate almost loss-less propagation of negatively refracted light in strongly absorbing gas at experimental parameters currently existing in many labs. *Location: **B-105* @ Center for Astrophysics (60 Garden Street <https://maps.google.com/?q=60+Garden+Street&entry=gmail&source=g>) *Directions: *After entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, B-105 will be the second room to the end of the hallway on the left side.

5 years, 6 months

[Aspuru-Guzik Group List] [qip] talks tomorrow

by Aram Harrow

Dear quanta, We will have no group meeting tomorrow. (Our next meeting will be Fri, Nov 9, and John Napp is speaking.) Instead, there are two talks that should interest many of us. 1. title: Quantum lightning never strikes the same state twice Friday, November 2, 2018 - 10:30am to 12:00pm Location: 32-G882 Speaker: Mark Zhandry, Princeton Abstract: Quantum no-cloning states that it is physically impossible to clone a quantum state. No-cloning is a central to the study of quantum cryptography, where it allows for objects such as physically unforgeable currency. In this work, I study two strong variants of no-cloning: (1) public key quantum money, where the would-be cloner is given a verification oracle for checking if it successfully cloned; and (2) quantum lightning, where the cloner even knows all the details of how the initial state was constructed. I then give a variety of results for public key quantum money and quantum lightning, yielding new constructions and interesting connections to other areas of cryptography. 2. title: Compass Codes Fri, Nov 2 - 1:30pm-2:30pm speaker: Ken Brown (Duke) abstract: The compass model of condensed-matter physics directly inspired the Bacon-Shor subsystem code, but both the Shor code and the rotated surface code can be considered as alternate choices for fixing gauge operators. I will discuss our work exploring the space of compass codes on LxL lattices and potential advantages over the surface codes for errors that are anisotropic or inhomogeneous in space. I will then focus on distance 3 versions of the compass code and describe their possible implementation with trapped atomic ions. This will include a discussion of stabilizer slicing for correcting systematic errors during syndrome extraction. _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

5 years, 6 months

[Aspuru-Guzik Group List] [qip] postdoc positions at UMD

by Ramis Movassagh

HI All, A colleague (Zohreh Davoudi, UMD Physics Professor) sent this and encouraged people to apply if interested and expertise in any subset of Quantum Computation Applications in Particle, Nuclear and Condensed-Matter Physics https://academicjobsonline.org/ajo/jobs/12398 Best, -- Ramis _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

5 years, 6 months

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aspuru-list November 2018