Quantum Nondemolition Detection of a Propagating Microwave Photon

Abstract

The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realizing such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon interactions in a waveguide have recently been demonstrated. Here we show how this type of interaction can be used to realize a quantum nondemolition measurement of a single propagating microwave photon. The scheme we propose uses a chain of solid-state three-level systems (transmons) cascaded through circulators which suppress photon backscattering. Our theoretical analysis shows that microwave-photon detection with fidelity around 90% can be realized with existing technologies. DOI: 10.1103/PhysRevLett.112.093601 PACS numbers: 42.50.Dv, 42.50.Lc, 42.65.-k, 85.60.Gz Quantum mechanics tells us that a measurement perturbs the state of a quantum system. In the most extreme case, this leads to the destruction of the measured quantum system. By coupling the system to a quantum probe, a quantum nondemolition [1] (QND) measurement can be realized, where the system is not destroyed by the measurement. Such a property is crucial for quantum error correction [2], state preparation by measurement [3,4], and one-way quantum computing [5]. For microwave frequencies, detection of confined photons in high-Q cavities has been proposed and experimentally demonstrated by several groups [6][7][8][9]. They all exploit the strong interaction between photons and atoms (real and artificial) on the single photon level. Detection schemes for traveling photons have also been suggested [10][11][12], but in those proposals the photon is absorbed by the detector and the measurement is therefore destructive. Proposals for detecting itinerant photons using coupled cavities have also been suggested, but they are limited by the trade-off between interaction strength and signal loss due to reflection [13]. Other schemes based on the interaction of Λ-type atomic level structures have been suggested, but the absence of such atomic level structures in solid-state systems make them unsuited to the microwave regime [14][15][16].Here, we present a scheme to detect a propagating microwave photon in an open waveguide. At its heart is the strong effective nonlinear interaction between microwave fields induced by an artificial atom to which they are coupled. A single photon in the control field induces a detectable displacement in the state of a probe field, which is initially in a coherent state. The control field is not absorbed, making the protocol QND. The protocol may be operated either synchronously (in which the control photons arrive within specified temporal windows) or asynchronously [17]. Figure 1 illustrates the scheme. The effective nonlinear interaction between the control photon and the probe field is realized by N noninteracting artificial atoms (transmon devices [18]) coupled to the tran...

Non-absorbing high-efficiency counter for itinerant microwave photons

“…For a single transmon, we report a SNR of 1.2, corresponding to a distinguishability of F = 84% between 0 and 1 photons in the signal (i.e., the probability of correctly discriminating between these two states). This can be improved using more transmons [15], and we show that with two cascaded transmons the distinguishably increases to F = 90%. An important feature of the proposal is that the signal photon is an itinerant photon pulse, enabling detection of relatively wide-band microwave photons.…”

“…This type of detection requires repeated measurements, and the high-Q cavity limits the photodetection bandwidth. In the microwave regime the detection of single photons [6][7][8][9][10][11][12][13][14][15] is more challenging, especially nondestructive detection [6,9,14,15]. Here we propose a scheme for nonabsorbing, high-efficiency detection of single itinerant microwave photons via the nonlinearity provided by an artificial superconducting atom, a transmon [16].…”

“…In the microwave regime the detection of single photons [6][7][8][9][10][11][12][13][14][15] is more challenging, especially nondestructive detection [6,9,14,15]. Here we propose a scheme for nonabsorbing, high-efficiency detection of single itinerant microwave photons via the nonlinearity provided by an artificial superconducting atom, a transmon [16].Previously [15,17], we considered schemes where the signal photon wave packet propagates freely in an open transmission line [11,18] and encounters the lowest transition of a transmon. The cw-probe field couples the first and second excited states of the transmon and is monitored via continuous homodyne detection.…”

“…Previously [15,17], we considered schemes where the signal photon wave packet propagates freely in an open transmission line [11,18] and encounters the lowest transition of a transmon. The cw-probe field couples the first and second excited states of the transmon and is monitored via continuous homodyne detection.…”

Quantum measurement and control in single-photon opto-mechanics

“…This formalism is introduced for a one-mode input field with Fock state master equation in supplementary material of [81]. In this subsection we exactly follow the one-mode procedure given in [81,82] to present the derivation for the two-mode input field. The goal is to calculate…”