Experimental demonstration of a Hadamard gate for coherent state qubits

Tipsmark, Anders; Dong, Ruifang; Laghaout, Amine; Marek, Petr; Ježek, Miroslav; Andersen, Ulrik L.

doi:10.1103/physreva.84.050301

Cited by 71 publications

(48 citation statements)

References 21 publications

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“…The setup used for the experimental test of the nonclassical character of photon-subtracted squeezed states [25] is shown in Fig. 3.…”

Section: Methodsmentioning

confidence: 99%

“…In this work, we are interested in the quantum nonGaussianity of approximate squeezed single-photon states obtained by photon subtraction from a squeezed vacuum [18][19][20][21][22][23][24][25]. In the ideal case of perfect single-photon subtraction from pure squeezed vacuum, we would obtain a pure squeezed single-photon state |ψ(r) = S(r)|1 , where the squeezing operation reads…”

Section: Quantum Non-gaussian Statesmentioning

confidence: 99%

“…In this paper, we experimentally certify the quantum nonGaussianity of a conditionally generated squeezed singlephoton state [18][19][20][21][22][23][24][25] whose Wigner function is positive at the origin of phase space due to noise. The state is prepared by conditionally subtracting a single photon from a squeezed vacuum state, and it is probed with a homodyne detector.…”

Section: Introductionmentioning

confidence: 99%

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Experimental test of the strongly nonclassical character of a noisy squeezed single-photon state

et al. 2012

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We experimentally verify the quantum non-Gaussian character of a conditionally generated noisy squeezed single-photon state with positive Wigner function. Employing an optimized witness based on probabilities of squeezed vacuum and squeezed single-photon states we prove that the state cannot be expressed as a mixture of Gaussian states. In our experiment, the non-Gaussian state is generated by conditional subtraction of a single photon from squeezed vacuum state. The state is probed with a homodyne detector and the witness is determined by averaging a suitable pattern function over the measured homodyne data. Our experimental results are in good agreement with a theoretical fit obtained from a simple yet realistic model of the experimental setup.

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“…The setup used for the experimental test of the nonclassical character of photon-subtracted squeezed states [25] is shown in Fig. 3.…”

Section: Methodsmentioning

confidence: 99%

Section: Quantum Non-gaussian Statesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental test of the strongly nonclassical character of a noisy squeezed single-photon state

et al. 2012

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“…We note that it is also possible to transform the state in (10) into |0 |α + |1 | − α using a Hadamard transformation on mode B. The Hadamard transform on coherent state superpositions can be implemented with linear optics and non-Gaussian resources [37,38], and has been experimentally demonstrated [39]. It is clear that for large excitations the two coherent states are macroscopically distinct in their quadrature degree of freedom.…”

Section: Coherent State Superpositionsmentioning

confidence: 99%

Heralded generation of a micro-macro entangled state

Andersen

Neergaard-Nielsen

2013

Phys. Rev. A

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Using different optical setups based on squeezed state and photon subtraction we show how optical entanglement between a macroscopic and a microscopic state-the so-called Schrödinger cat state or micro-macro state-can be generated. The entangled state is heralded and is thus produced a priori in contrast to previous proposals. We define the macroscopicity of the macroscopic part of the state as their mean distance in phase space and the success rate in discriminating them with homodyne detection, and subsequently, based on these measures we investigate the macroscopicity of different states. Furthermore, we show that the state can be used to map a microscopic qubit onto a macroscopic one thereby linking a qubit processor with a qumode processor.

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“…Depending on the chosen configuration one can either conditionally prepare a Fock state [10,11] or perform a conditional single-photon addition [12,13] or subtraction [14][15][16][17][18]. These latter operations proved to be extremely powerful and useful in engineering various quantum states and operations [19][20][21][22][23][24]. In particular, by conditionally subtracting a single photon from a squeezed vacuum state one can generate a squeezed single-photon state that closely approximates a coherent superposition of two coherent states, also referred to as Schrödinger cat-like state.…”

Section: Introductionmentioning

confidence: 99%

Witnessing negativity of Wigner function by estimating fidelities of catlike states from homodyne measurements

Fiurášek

Ježek

2013

Phys. Rev. A

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We derive sampling functions for estimation of quantum state fidelity with Schrödinger catlike states, which are defined as superpositions of two coherent states with opposite amplitudes.We also provide sampling functions for fidelity with squeezed Fock states that can approximate the cat-like states and can be generated from Gaussian squeezed states by conditional photon subtraction. The fidelities can be determined by averaging the sampling functions over quadrature statistics measured by homodyne detection. The sampling functions are designed such that they can compensate for losses and inefficient homodyning provided that the overall efficiency exceeds certain threshold. The fidelity with an odd coherent state and the fidelity with a squeezed odd Fock state provide convenient witnesses of negativity of Wigner function of the measured state.The negativity of Wigner function at the origin of phase space is certified if any of these fidelities exceeds 0.5. Finally, we discuss the possibility of reducing the statistical uncertainty of the fidelity estimates by a suitable choice of the dependence of the number of quadrature samples on the relative phase shift between local oscillator and signal beam.

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Experimental demonstration of a Hadamard gate for coherent state qubits

Cited by 71 publications

References 21 publications

Experimental test of the strongly nonclassical character of a noisy squeezed single-photon state

Experimental test of the strongly nonclassical character of a noisy squeezed single-photon state

Heralded generation of a micro-macro entangled state

Witnessing negativity of Wigner function by estimating fidelities of catlike states from homodyne measurements

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