Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E46: Remote Entanglement with Superconducting QubitsFocus

Hide Abstracts 
Sponsoring Units: GQI Chair: Mollie KimchiSchwartz, MIT Lincoln Laboratory Room: 393 
Tuesday, March 14, 2017 8:00AM  8:36AM 
E46.00001: Robust, modular entanglement of two remote superconducting qubits Invited Speaker: Shyam Shankar Superconducting quantum circuits are a leading platform for quantum computing, however scaling up to larger size systems is an open challenge. A potential pathway to scaling is provided by the modular quantum computing architecture. In this architecture, small modules consisting of a few qubits and cavity modes are optimized for a specific function, separately tested and then connected in a manner that prevents crosstalk between modules. A key primitive for this architecture is the ability to entangle two remote quantum systems that never interact directly. I will present our recent experimental realization of remote, modular entanglement of two superconducting qubits that is robust to imperfections in the connections between modules. Our implementation achieves an entanglement fidelity of 0.57 at a rate of 200 Hz. I will then discuss our efforts to improve the fidelity and generation rate in order to implement entanglement distillation. [Preview Abstract] 
Tuesday, March 14, 2017 8:36AM  8:48AM 
E46.00002: Threequbit remote entanglement by joint measurement and feedback control Song Zhang, Leigh Martin, K. Birgitta Whaley For remote qubits, a direct nonlocal interaction is generally not available, in part because the coherence of any transmitted signal is degraded by loss. In this situation, joint measurement and feedback control nevertheless allow creation of entanglement between remote qubits. Such schemes are known for deterministic generation of Bell states, but the generalization to larger systems has not been studied. We present such a control protocol based on the average sense local optimality (ASLO) approach for generating entanglement in a threequbit system without an entangling Hamiltonian. Analytical and numerical methods to enhance the generation of different types of threequbit entanglement are presented. [Preview Abstract] 
Tuesday, March 14, 2017 8:48AM  9:00AM 
E46.00003: Chiptochip entanglement of transmon qubits Christian Dickel, Sarwan Peiter, Ramiro Sagastizabal, Nathan Langford, Ben Criger, David Thoen, Akira Endo, Alessandro Bruno, Leonardo DiCarlo We realize entanglementbymeasurement of two superconducting transmon qubits on separate 2D circuit QED chips. Two qubitresonator pairs are tuned such that a microwave driving field bouncing successively from the two resonators does not distinguish the two oddparity states of the qubits [1]. Thus, a halfparity measurement is realized, projecting the qubits onto the $\vert 00 \rangle$ state, the $\vert 11 \rangle$ state or the odd subspace. We use it to project an initial superposition state to a Bell state. The entanglementbymeasurement dynamics are verified via quantum state tomography. Conditioning the postmeasurement state on the oddsubspace measurement outcome shows clear signatures of entanglement. Engineering the timedependent resonator driving fields can reduce the distinguishability within the odd subspace, improving the entanglement. This scheme enables linking up 2D circuit QED processors in a quantum network. [1] N. Roche et al., Phys. Rev. Lett. 112, 170501 (2014) [Preview Abstract] 
Tuesday, March 14, 2017 9:00AM  9:12AM 
E46.00004: Hardwareefficient Bell state preparation using Quantum Zeno Dynamics in superconducting circuits. Emmanuel Flurin, Machiel Blok, Shay HacohenGourgy, Leigh S. Martin, William P. Livingston, Allison Dove, Irfan Siddiqi By preforming a continuous joint measurement on a two qubit system, we restrict the qubit evolution to a chosen subspace of the total Hilbert space. This extension of the quantum Zeno effect, called Quantum Zeno Dynamics, has already been explored in various physical systems such as superconducting cavities, single rydberg atoms, atomic ensembles and Bose–Einstein condensates. In this experiment, two superconducting qubits are strongly dispersively coupled to a highQ cavity ($\chi\gg\kappa$) allowing for the doubly excited state $11\rangle$ to be selectively monitored. The Quantum Zeno Dynamics in the complementary subspace enables us to coherently prepare a Bell state. As opposed to dissipation engineering schemes, we emphasize that our protocol is deterministic, does not rely direct coupling between qubits and functions only using single qubit controls and cavity readout. Such Quantum Zeno Dynamics can be generalized to larger Hilbert space enabling deterministic generation of manybody entangled states, and thus realizes a decoherencefree subspace allowing alternative noiseprotection schemes. [Preview Abstract] 
Tuesday, March 14, 2017 9:12AM  9:24AM 
E46.00005: Robust quantum state transfer without impedance matching Mengzhen Zhang, Changling Zou, Liang Jiang Quantum state transfer is essential for building scalable quantum networks. Utilizing the ability of transferring quantum states between different frequency domains, people can combine the advantages of microwave and optical quantum processing and communication units. Many protocols aimed at achieving perfect continuous variable quantum state transfer are based on impedance matching condition, which is not always available in practical experiments and is usually constrained by bandwidth of the device. We come up with a new perfect state transfer scheme without this limitation. By utilizing squeezed modes, homodyne measurement and feedforward, we show perfect quantum state transfer is almost always achievable for an arbitrary linear unitary transformation process. We find this protocol is robust against practical imperfections and can be applied to various kinds of bosonic coupling systems. [Preview Abstract] 
Tuesday, March 14, 2017 9:24AM  9:36AM 
E46.00006: Deterministic Creation of an InterChip Bell State without Feedback James Wenner, C. Neill, Z. Chen, B. Chiaro, A. Dunsworth, B. Foxen, C. Quintana, John M. Martinis Creating Bell states between qubits on separate chips deterministically and without feedback requires the transfer of quantum states via a traveling photonic mode. Efficient transfer requires a shaped release to the photonic mode and managing the capture of this mode to minimize reflections. We implement this using 5GHz coplanar resonators on separate chips with tunable coupling to an interchip transmission line. We characterize the device coherence and demonstrate the ability to release a singlefrequency shaped pulse into the transmission line and efficiently capture a shaped pulse. By combining these, we transfer single qubit states along with the singlequbit half of a Bell state with optimallyshaped transfer waveforms. We achieve a 68\% fidelity for the interchip Bell state. This interchip entanglement will allow for quantum computation using more qubits beyond what fits on a single chip. [Preview Abstract] 
Tuesday, March 14, 2017 9:36AM  9:48AM 
E46.00007: Schrodinger's catapult I: coherent launch of multiphoton cavity states C. Axline, W. Pfaff, L. D. Burkhart, U. Vool, P. C. Reinhold, L. Frunzio, L. Jiang, M. H. Devoret, R. J. Schoelkopf Quantum networks are a powerful paradigm for managing complexity in quantum information processing. Here we present a circuit QED tool to control the exchange of quantum information in such a network, dubbed "Schrodinger's catapult". It enables rapid conversion between complex, multiphoton states prepared in a cavity memory and a propagating output mode. Enabled by fourwave mixing in a single Josephson junction, this conversion rate is tunable up to three orders of magnitude faster than the intrinsic memory decay rate. In addition to such a large on/off ratio, we show that the mapping of cavity states to traveling states is faithful and stateindependent. Amplitude and phase control of the conversion process anticipates the capture of propagating states using a reciprocal module. [Preview Abstract] 
Tuesday, March 14, 2017 9:48AM  10:00AM 
E46.00008: Schrodinger's catapult II: entanglement between stationary and flying fields W. Pfaff, C. Axline, L. Burkhart, U. Vool, P. Reinhold, L. Frunzio, L. Jiang, M. Devoret, R. Schoelkopf Entanglement between nodes is an elementary resource in a quantum network. An important step towards its realization is entanglement between stationary and flying states. Here we experimentally demonstrate entanglement generation between a longlived cavity memory and traveling mode in circuit QED. A large on/off ratio and fast control over a parametric mixing process allow us to realize conversion with tunable magnitude and duration between standing and flying mode. In the case of halfconversion, we observe correlations between the standing and flying state that confirm the generation of entangled states. We show this for both singlephoton and multiphoton states, paving the way for errorcorrectable remote entanglement. Our system could serve as an essential component in a modular architecture for errorprotected quantum information processing. [Preview Abstract] 
Tuesday, March 14, 2017 10:00AM  10:12AM 
E46.00009: Temporal shaping of quantum states released from a superconducting cavity memory L. Burkhart, C. Axline, W. Pfaff, C. Zou, M. Zhang, A. Narla, L. Frunzio, M.H. Devoret, L. Jiang, R.J. Schoelkopf State transfer and entanglement distribution are essential primitives in networkbased quantum information processing. We have previously demonstrated an interface between a quantum memory and propagating light fields in the microwave domain: by parametric conversion in a single Josephson junction, we have coherently released quantum states from a superconducting cavity resonator into a transmission line. Protocols for state transfer mediated by propagating fields typically rely on temporal modematching of couplings at both sender and receiver. However, parametric driving on a single junction results in dynamic frequency shifts, raising the question of whether the pumps alone provide enough control for achieving this modematching. We show, in theory and experiment, that phase and amplitude shaping of the parametric drives allows arbitrary control over the propagating field, limited only by the drives’ bandwidth and amplitude constraints. This temporal mode shaping technique allows for release and capture of quantum states, providing a credible route towards state transfer and entanglement generation in quantum networks in which quantum states are stored and processed in cavities. [Preview Abstract] 
Tuesday, March 14, 2017 10:12AM  10:24AM 
E46.00010: Deterministic teleportation of a twoqubit quantum gate in circuit QED: Part 1 K Chou, J Z Blumoff, C S Wang, P Reinhold, L Frunzio, M H Devoret, L Jiang, R J Schoelkopf An important consideration for scaling quantum information processing is to minimize unwanted interactions among parts of the quantum computer. This problem is simplified in a modular architecture, where isolated registers containing a few wellcontrolled degrees of freedom are connected through a limited number of quantum links. To effect a quantum algorithm using this architecture, one can utilize teleported gates between modules. These gates require an ancillary entangled pair as a resource, highfidelity local operations within the registers and measurements of the ancillary qubits, and realtime feedback. In our work, we have fulfilled these requirements in a circuit QED system to implement a CNOT operation between two qubits which do not directly interact, where the qubits are encoded in the states of two harmonic oscillators. In this first of two talks, we discuss our approach and design considerations toward realizing this teleported CNOT operation. [Preview Abstract] 
Tuesday, March 14, 2017 10:24AM  10:36AM 
E46.00011: Deterministic teleportation of a twoqubit quantum gate in circuit QED: Part 2 J Z Blumoff, K Chou, C S Wang, P Reinhold, L Frunzio, M H Devoret, L Jiang, R J Schoelkopf A modular architecture of superconducting circuit QED devices has been proposed as a path towards scalable quantum information processing. In this approach, the quantum computer consists of small, wellunderstood quantum registers that are networked through a limited number of quantum links. Gates via these links can be performed by quantum teleportation, requiring an ancillary entangled pair as a resource, highfidelity local operations within the registers and measurements of the ancillary qubits, and realtime feedback. In our work, we have fulfilled these requirements in a circuit QED system to implement a CNOT operation between two qubits which do not directly interact, where the qubits are encoded in the states of two harmonic oscillators. In this second of two talks, we discuss our experimental results and outlook. [Preview Abstract] 
Tuesday, March 14, 2017 10:36AM  10:48AM 
E46.00012: Towards entanglement purification in circuit QED C S Wang, J Z Blumoff, K Chou, P Reinhold, L Frunzio, M H Devoret, L Jiang, R J Schoelkopf An attractive approach toward scaling a quantum computer is the modular architecture, where isolated registers containing a few wellcontrolled degrees of freedom are connected through a limited number of quantum links. These links enable gates between registers via teleportation, a protocol which requires an interregister entangled pair as a resource. If these links are of lower quality, we can still create a highfidelity entangled pair by utilizing entanglement purification. We will discuss our implementation for purification of entanglement between qubits encoded in the state of two noninteracting superconducting cavities. In this talk, we describe the experimental protocol and report our results toward realizing such a scheme. [Preview Abstract] 
Tuesday, March 14, 2017 10:48AM  11:00AM 
E46.00013: Remote entanglement stabilization for modular quantum computing Nicolas Didier, S. Shankar, M. Mirrahimi Quantum information processing in a modular architecture requires to distribute and stabilize entanglement in a qubit network. We present autonomous entanglement stabilization protocols between two qubits that are coupled to distant cavities. The cavities coupling is mediated and controlled via a threewave mixing device that generates either a delocalized mode or a twomode squeezed state between the remote cavities depending on the pump frequency. Local drives on the qubits and the cavities steer and maintain the system to the desired qubit Bell state. We show that these reservoirengineering based protocols stabilize entanglement in presence of qubitcavity asymmetries and losses. Most spectacularly, even a weaklysqueezed state can stabilize a maximally entangled Bell state of two distant qubits through entanglement accumulation. [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2020 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700