Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session F39: Microwave Photonics with Superconducting Circuits IIFocus

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Sponsoring Units: DQI Chair: Michael Hatridge, Univ of Pittsburgh Room: LACC 501B 
Tuesday, March 6, 2018 11:15AM  11:51AM 
F39.00001: Microwave activated twophoton transition for remote entanglement of superconducting circuits Invited Speaker: Phillipe CampagneIbarcq , Evan ZalysGeller , Anirudh Narla , Shyam Shankar , Christopher Axline , Luke Burkhart , Wolfgang Pfaff , Philip Reinhold , Luigi Frunzio , Robert Schoelkopf , Michel Devoret Building a large scale quantum computing platform or network will most probably require to entangle distant systems that do not interact directly. This can be done by performing entangling gates between standing information carriers, used as memories or local computationnal resources, and flying ones, acting as quantum buses. In this talk, we report the realization of such gates between superconducting circuits and traveling microwave photons based on microwave activated twophoton transitions. We have implemented this protocol in a superconducting circuit architecture. Temporal and, to some extent, frequential shaping of the traveling wavepacket have been applied. We demonstrate both an entangling gate corresponding to the emission of a shaped photon conditionned on the excitation of a circuit and a swap gate corresponding to the absorption of this photon by a distant circuit. Combining both, we remotely entangle two transmon qubits with a Bell state fidelity of 73 %, limited by losses in the transmission line and decoherence of each qubit. 
Tuesday, March 6, 2018 11:51AM  12:27PM 
F39.00002: Deterministic Quantum State Transfer and Generation of Remote Entanglement using Microwave Photons Invited Speaker: Andreas Wallraff Sharing information coherently between nodes of a quantum network is at the foundation of distributed quantum information processing. In this scheme, the computation is divided into subroutines and performed on several smaller quantum registers connected by classical and quantum channels. A direct quantum channel, which connects nodes deterministically rather than probabilistically, is advantageous for faulttolerant quantum computation because it reduces the threshold requirements and can achieve larger entanglement rates. Here, we implement deterministic state transfer and entanglement protocols between two superconducting qubits [1] fabricated on separate chips [2] and connected by about one meter of coaxial cable with well characterized loss [3]. Superconducting circuits constitute a universal node capable of sending, receiving, storing, and processing quantum information. Our implementation is based on an allmicrowave cavityassisted Raman process which entangles or transfers the qubit state of a transmontype artificial atom with a timesymmetric itinerant single photon [4]. We transfer qubit states at a rate of 50 kHz using the emitted photons which are absorbed at the receiving node with a probability of 98\% achieving a transfer process fidelity of 80\%. We also prepare on demand remote entanglement with a fidelity as high as 79\%. Our results are in excellent agreement with a numerical simulations based on a master equation description of the system. Deterministic state transfer protocols have the potential to be used as a backbone of surface code quantum error correction across different nodes of a cryogenic network to realize large scale faulttolerant quantum computation. It is also interesting to consider augmenting the methods presented in this work by quantumnondemolition detection of single photons [5].\newline\newline [1] P. Kurpiers et al., arXiv:1712.08593 (2017)\newline [2] T. Walter et al., Phys. Rev. Applied 7, 054020 (2017)\newline [3] P. Kurpiers et al., EPJ Quantum Technology 4, 8 (2017)\newline [4] M. Pechal et al., Phys. Rev. X 4, 041010 (2014)\newline [5] J.C. Besse et al., arXiv:1711.11569 (2017) 
Tuesday, March 6, 2018 12:27PM  12:39PM 
F39.00003: Distilling Entanglement Between Remote Superconducting Qubits Evan ZalysGeller , Philippe CampagneIbarcq , Anirudh Narla , Shyam Shankar , Christopher Axline , Luke Burkhart , Wolfgang Pfaff , Luigi Frunzio , Robert Schoelkopf , Michel Devoret The ability to generate entanglement between qubits connected by a lossy channel is an important primitive for large scale quantum information processing. Entanglement distillation allows one to counter this imperfection by consolidating the entanglement between several weakly entangled qubit pairs into a single strongly entangled qubit pair. We present an experiment where we can generate remote entanglement between two nodes, each containing a pair of superconducting transmon qubits, with matching dispersive shifts to their respective cavities. By performing local halfparity measurements, we can detect photon loss in the channel connecting the nodes, and herald the creation of a Bell state with enhanced fidelity. We discuss experimental progress towards the implementation of this protocol. 
Tuesday, March 6, 2018 12:39PM  12:51PM 
F39.00004: Remote communication between two superconducting qubit modules 1 Nelson Leung , Yao Lu , Srivatsan Chakram , Ravi Naik , Nathan Earnest , Robert Cook , Kurt Jacobs , Andrew Cleland , David Schuster We extend the random access quantum processor module [1] to allow photonic communication between two distant modules. Each module comprises of 8bit multimode resonators and a fluxtunable transmon. The sideband interaction induced by the transmon flux modulation achieves both the universal operations on each quantum processor and the photonic communication between two modules. Entanglement between two distant modules can be created by a transfer process heralded to photon loss during the transmission. Our implementation opens a clear path towards modular architecture of quantum information processing with superconducting qubits. 
Tuesday, March 6, 2018 12:51PM  1:03PM 
F39.00005: Remote communication between two superconducting qubit modules 2 Yao Lu , Nelson Leung , Srivatsan Chakram , Ravi Naik , Nathan Earnest , Robert Cook , Kurt Jacobs , Andrew Cleland , David Schuster We report our experimental progress towards implementing a heralding protocol for the transfer of an arbitrary qubit state between two distant superconducting qubits. We employ sideband interactions induced by parametric flux modulation for the preparation of locally entangled qubitphoton states, as well as for their transfer that generates entanglement between two distant superconducting qubits. As an useful application, we demonstrate how Bell states can be created between the two remote qubits via this technique. Through encoding a qubit state with two flying microwave photons, photon loss error can be heralded by the measurement of the receiving qubit, without the need of using ancillary qubits. This simple and efficient communication protocol provides a promising approach for realizing a scalable quantum network processor using the quantum computation modules as building blocks. 
Tuesday, March 6, 2018 1:03PM  1:15PM 
F39.00006: Deterministic Generation of Remote Entanglement using Shaped Single Photons in Circuit Quantum Electrodynamics Philipp Kurpiers , Paul Magnard , Theo Walter , Marek Pechal , Baptiste Royer , Johannes Heinsoo , Yves Salathe , Abdulkadir Akin , Simon Storz , JeanClaude Besse , Simone Gasparinetti , Alexandre Blais , Andreas Wallraff Sharing information coherently in a quantum network is the foundation of quantum communication and distributed quantum information processing. Here, we discuss our progress toward implementing a deterministic quantum state transfer and remote entanglement protocol in a circuit QED architecture. We embed a superconducting transmontype three level system in a transmission line resonator at two spatially separated nodes. We generate an itinerant shaped microwave photon based on a microwave drive induced secondorder process [1] and transmit it via a coaxial line [2]. Emitting and absorbing the single photon with high fidelity ideally achieves coherent qubit state transfer or remote entanglement generation. Our experiments, therefore, suggest a path toward realizing allmicrowave quantum networks based on deterministic interactions between individual nodes. 
Tuesday, March 6, 2018 1:15PM  1:27PM 
F39.00007: Detailed analysis of spontaneous emission of an atom in front of a mirror Emely Wiegand , Göran Johansson The spontaneous emission rate of a twolevel atom is proportional to the local density of states of the electromagnetic modes of the environment close to its transition frequency. 
Tuesday, March 6, 2018 1:27PM  1:39PM 
F39.00008: Deterministic Generation of a Traveling Cat State with a Kerr Parametric Oscillator Hayato Goto , Zhirong Lin , Tsuyoshi Yamamoto , Yasunobu Nakamura Quantum computation with a network of Kerr parametric oscillators, or KPOs for short, has been proposed for the standard gate model [1,2] and adiabatic optimization [3]. Such a new machine is expected to be implemented with superconducting circuits [4,5]. A remarkable feature of a KPO is the ability to generate a Schödinger cat state deterministically via quantum adiabatic evolution. However, the cat state inside the KPO seems difficult to observe because of the large Kerr effect. Here we theoretically propose a method to release the cat state from the KPO without a tunable output coupler. As a result, a traveling cat state can be generated deterministically with a KPO and observed, e.g., by homodyne detection. We will also propose a superconductingcircuit implementation of the travelingcat generator. 
Tuesday, March 6, 2018 1:39PM  1:51PM 
F39.00009: Full Kerr Cancellation in an InductivelyShunted Josephson Ring Modulator Xi Cao , TzuChiao Chien , Olivia Lanes , Gangqiang Liu , David Pekker , Michael Hatridge Quantumlimited amplification plays a vital role in efficient quantum measurement. For superconducting qubits, such amplification can be achieved through parametrically driven threewave mixing in the Josephson Ring Modulator (JRM). However, we have shown that Kerr nonlinearities in and between the JRM’s modes limit the device’s saturation power and jeopardize frequency matching conditions for multiply parametric driven modes of operation. We present a JRM shunted with linear inductors [1] which, for a range of parameters, cancels all the Kerr terms at a certain flux bias point while retaining threewave mixing terms. The stability of this special bias point depends crucially on the ratio of shunt inductance to Josephson junction inductance as well as stray inductance in the JRM ring itself. We present both self and crossKerr measurements showing simultaneous cancellation as well as the absence of fourthorder behaviors in the amplifier’s response to large signal powers. This device, in addition to enhanced saturation power is expected to be an excellent candidate for multiplydriven parametric devices. 
Tuesday, March 6, 2018 1:51PM  2:03PM 
F39.00010: Driveenhanced Superradiance in Circuit QED Catherine Leroux , Luke Govia , Aashish Clerk We recently analyzed theoretically how twophoton driving of a cavity could be used to exponentially enhance the lightmatter coupling in a cavity QED system, allowing a weak coupling system to exhibit features of ultrastrong coupling [1]. Here, we extend this idea to a system where an ensemble of twolevel systems couple weakly to a cavity. We discuss how the superradiant phase transition manifests itself in this system, and how it is sensitive to the structure of the input noise driving the cavity. We discuss potential implementations using superconducting circuits, where simple fluxpumping provides the necessary driving. Our scheme allows for a tuneable analog quantum simulation of the opensystem Dicke model. [1] C. Leroux, L. C. G. Govia, and A. A. Clerk, arXiv:1709.09091. 
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