Optically based analog-to-digital converter

Abstract

The invention relates to an optically based analog-to-digital converter (1) comprising • a first combiner (C1) with a first input (I1) for an optical reference signal (Ref) and a second input (I2) for an input signal to be digitized, • a second combiner (C2) with a first input (I3) for a pulsed laser signal and a second input (I4) connected to the output of the first combiner (C1), • an evaluation unit (AE) which evaluates the output signal of the second combiner (C2), • characterized in that the evaluation unit (AE) has a quantum pulse gate (QPG).

Description

[0001] The invention relates to an optically based analog-to-digital converter. background

[0002] In many areas, data is acquired using analog sensors and transformed into a digital format for processing. This is done using so-called analog-to-digital converters (ADCs), sometimes also referred to as analog-to-digital converters.

[0003] One problem with existing analog-to-digital converters is their internal noise. Furthermore, due to internal distortion of the desired signal, the resolution accuracy of existing analog-to-digital converters is limited by the maximum number of effective bits (ENOBs).

[0004] In the past, there have been attempts to address these problems.

[0005] For example, the article “Photonic-Assisted Analog-to-Digital Conversion Based on a Dispersion-Diversity Multicore Fiber” by S. Garcia, M. Ureña and I. Gasulla, published in IEEE Journal of Selected Topics in Quantum Electronics, vol. 29, no. 6: Photonic Signal Processing, pp. 1-8, Nov.-Dec. 2023, presents the concept of a photonically assisted ADC whose optical input signal was split into differently delayed paths using true time delay lines (TTDL), and these were then detected using photodiodes.

[0006] Furthermore, a photonically supported electronic track & hold ADC is known from the article “Optically Enabled ADCs and Application to Optical Communications” by the authors A. Zazzi et al., published in IEEE Open Journal of the Solid-State Circuits Society, vol. 1, pp. 209-221, 2021, whose clock signal was provided by manipulating a pulsed laser signal.

[0007] Also known from the article “A Cryogenic 1 GSa / s, Soft-Core FPGA ADC for Quantum Computing Applications” by the authors H. Homulle, S. Visser and E. Charbon, published in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 63, no. 11, pp. 1854-1865, Nov. 2016, is an ADC concept for quantum applications in which the ADC is implemented in a Field Programmable Gate Array (FPGA) and this has to be cooled down to cryogenic temperatures in a complex process.

[0008] Furthermore, the article “A Cryogenic 8-Bit 32 MS / s SAR ADC Operating down to 4.2 K” by the authors Y. Huang, C. Luo, and G. Guo, published in Electronics, Vol. 12, No. 6, describes an electronic ADC for quantum applications that also requires complex cooling to cryogenic temperatures.

[0009] While the known approaches represent an improvement, they are not able to sustainably and cost-effectively solve the problems (internal noise as well as internal distortion), so the resolution accuracy of the analog signal remains limited.

[0010] US patent application US 2022 / 0149949A1 shows a signal processing unit.

[0011] Starting from this situation, the object of the invention is to provide an optically based analog-to-digital converter that makes it possible to digitize arbitrarily high analog signals with high resolution accuracy, low distortion and low internal noise.

[0012] The problem is solved by an optically based analog-to-digital converter according to claim 1. Further advantageous embodiments are in particular the subject of the dependent claims.

[0013] The invention is explained in more detail below with reference to the figures. These show: Fig. 1 schematically the basic principle of the quantum-assisted ADC according to embodiments of the invention, Fig. 2 schematically the basic principle of the quantum-assisted ADC according to embodiments of the invention for an electrical input signal, Fig. 3 schematically the basic principle of the quantum-assisted ADC according to embodiments of the invention, in that the reference signal is generated on the basis of the pulsed laser signal, Fig. 4 schematically the basic principle of the quantum-assisted ADC according to embodiments of the invention for an electrical input signal, wherein both the reference signal and the input signal of the EO converter can be generated by means of OPO based on the pulsed laser signal, Fig. 5 schematically the basic principle of the quantum-assisted ADU according to embodiments of the invention with CW laser and pulse-shaping element, and Fig. Figure 6 schematically illustrates the basic principle of the quantum-assisted ADC according to embodiments of the invention for an electrical input signal. Here, the input signal of the OE modulator and the reference signal originate from the same source.

[0014] The invention will now be described in more detail with reference to the figures. It should be noted that different aspects are described, each of which can be used individually or in combination. That is, each aspect can be used with different embodiments of the invention unless explicitly presented as a pure alternative.

[0015] Furthermore, for the sake of simplicity, reference will generally be made to only one entity at a time. Unless explicitly stated otherwise, the invention may also include several of the entities concerned. Therefore, the use of the words "a," "an," and "a" should only be understood as an indication that at least one entity is used in a simple embodiment.

[0016] Unless explicitly stated otherwise, the individual steps of a procedure described below can be arranged and / or combined in any order. Furthermore, unless expressly indicated otherwise, the procedures can be combined with one another.

[0017] Information with numerical values ​​should generally not be understood as exact values, but also include a tolerance of + / - 1% to + / - 10%.

[0018] References to standards or specifications are to be understood as references to standards or specifications that are valid or were valid at the time of filing and / or – insofar as priority is claimed – at the time of the priority filing. However, this does not imply a general exclusion of applicability to subsequent or superseding standards or specifications.

[0019] Fig. show exemplary embodiments of the invention.

[0020] In embodiments of the invention, an optically based analog-to-digital converter 1 is provided.

[0021] The basic principle of the invention is in Fig. demonstrated and works according to the principle from the article "Achieving the Ultimate Quantum Timing Resolution" by the authors Vahid Ansari, Benjamin Brecht, Jano Gil-Lopez, John M. Donohue, Jaroslav Rehacek, Zdenek Hradil, Luis L. Sanchez-Soto, and Christine Silberhorn, published in 2021-01 PRX Quantum, Vol. 2 American Physical Society p. 010301.

[0022] The optically based analog-to-digital converter 1 according to the invention has a first combiner C1 with a first input I1 for an optical reference signal Ref and a second input I2 for an input signal Analog to be digitized.

[0023] Furthermore, the optically based analog-to-digital converter 1 according to the invention has a second combiner C2 with a first input I3 for a pulsed laser signal and a second input I4, which is connected to the output of the first combiner C1.

[0024] Furthermore, the optically based analog-to-digital converter 1 according to the invention has an evaluation unit AE which evaluates the output signal of the second combiner C2.

[0025] In the invention, two optical signals, the reference signal Ref and the analog signal (to be digitized), are superpositioned in the first combiner C1 during operation. The amplitude of the reference signal is known.

[0026] This superposition of the two input signals, along with a shaped pulse, is fed into an evaluation unit (AE). The output signal of the evaluation unit (AE) can then be used to draw conclusions about the intensity differences.

[0027] By evaluating the measured signal and the already known reference signal, the value of the analog signal can be determined.

[0028] A clock for temporal quantization can be provided via the pulsed laser signal.

[0029] In embodiments of the invention, see e.g. Fig. 2, Fig. 3 or Fig. 6, an optical modulator MOD is arranged in front of the input for the input signal to be digitized, which modulates an optical input signal by means of the input signal to be digitized.

[0030] In one embodiment of the invention, an electro-optical modulator MOD is arranged upstream of the input I2 for the input signal to be digitized, which modulates an optical input signal by means of the input signal to be digitized, wherein the input signal to be digitized is an electrical signal.

[0031] That is, if the signal to be digitized is in analog form as an electrical signal, the electrical signal can be converted into an optical signal using the optical modulator MOD. The design of the optical modulator can be appropriately selected by a specialist.

[0032] In the embodiment according to Fig. 3 A first splitter SP1 is arranged upstream of the electro-optical modulator MOD, which splits an optical input signal, wherein a first part of the optical input signal is made available to the electro-optical modulator MOD during operation and a second part of the optical input signal is fed to the first input I1 of the first combiner C1 as a reference signal Ref during operation.

[0033] In one embodiment of the invention - see Fig. 3 and Fig. 4 - The reference signal can also be generated using an optical parametric oscillator (OPO) based on the pulsed laser signal of the source (PL). In one embodiment, both the reference signal and the input signal of the EO modulator (MOD) can be generated using an optical parametric oscillator (OPO) based on the pulsed laser signal (PL).

[0034] According to a further embodiment of the invention, an RF laser is arranged in front of the input I2 for the input signal to be digitized, which is controlled by means of the input signal to be digitized, wherein the input signal to be digitized is an electrical signal.

[0035] That is, it is also possible that an analog electrical signal to be digitized can also be directly converted into an optical signal using an RF laser.

[0036] According to yet another embodiment of the invention - see Fig. 2 - the optical reference signal Ref can also be provided by a second CW laser CW2.

[0037] In one embodiment of the invention, a pulse shaper PS can be arranged in front of the input I3 for the pulsed laser signal (see figures).

[0038] In another embodiment of the invention, the input signal for the pulse shaper PS is provided by a pulsed laser PL - see Fig. 1-4 and 6 - or from a first CW laser CW1 with subsequent pulse shaper PF - see Fig. 6 - provided.

[0039] According to a further embodiment of the invention, a second splitter SP2 is arranged directly in front of the pulse shaper PS - see Fig. 3 and Fig. 4 -, wherein a first part of the optical input signal from the second splitter SP2 is provided to the pulse shaper PS during operation, and a second part of the optical input signal is fed via an optical parametric oscillator OPO to the first input I1 of the first combiner C1 as a reference signal Ref.

[0040] According to the invention, the evaluation unit AE comprises a quantum pulse gate QPG. In particular, the quantum pulse gate QPG can also be a multi-output quantum pulse gate.

[0041] Similarly, in one embodiment of the invention, the quantum pulse gate (QPG) may have a polarized nonlinear waveguide. The polarization can be either periodic or aperiodic.

[0042] In a further embodiment of the invention, the quantum pulse gate (QPG) comprises a periodically polarized lithium niobate waveguide or a polarized potassium titanyl phosphate waveguide. The polarization can be either periodic or aperiodic.

[0043] Furthermore, in one embodiment of the invention, it may be provided that the evaluation unit AE comprises at least one optoelectronic conversion unit OE, e.g. a photodiode or a phototransistor.

[0044] In a further embodiment of the invention, the evaluation unit AE further comprises a first optical bandpass filter BP1.

[0045] According to yet another embodiment, the optically based analog-to-digital converter 1 is fully integrated, or partially integrated, or implemented with discrete components.

[0046] The invention provides an analog-to-digital converter that makes it possible to digitize arbitrarily high analog optical as well as electrical signals with high resolution accuracy, low distortion and low internal noise.

[0047] The analog-to-digital converter according to the invention is limited in its resolution accuracy solely by quantum noise. This overcomes the disadvantages of current state-of-the-art technology with regard to resolution accuracy. Furthermore, the ADC can also be used for quantum applications without requiring cryogenic cooling.

Claims

[1] Optically based analog-to-digital converter (1) comprising • A first combiner (C1) with a first input (I1) for an optical reference signal and a second input (I2) for an input signal to be digitized, • A second combiner (C2) having a first input (I3) for a pulsed laser signal and a second input (I4) connected to the output of the first combiner (C1), • an evaluation unit (AE) which evaluates the output signal of the second combiner (C2), • characterized by that the evaluation unit (AE) has a quantum pulse gate (QPG). [2] Optically based analog-to-digital converter (1) according to claim 1, characterized by that an optical modulator (MOD) is arranged in front of the input for the input signal to be digitized, which modulates an optical input signal by means of the input signal to be digitized. [3] Optically based analog-to-digital converter (1) according to claim 1 or 2, characterized by that an electro-optical modulator (MOD) is arranged in front of the input (I2) for the input signal to be digitized, which modulates an optical input signal by means of the input signal to be digitized, wherein the input signal to be digitized is an electrical signal. [4] Optically based analog-to-digital converter (1) according to claim 3, characterized by in that a first splitter (SP1) is arranged in front of the electro-optical modulator (MOD), which splits an optical input signal, wherein a first part of the optical input signal is made available to the electro-optical modulator (MOD) during operation and a second part of the optical input signal is fed to the first input (I1) of the first combiner (C1) as a reference signal during operation. [5] Optically based analog-to-digital converter (1) according to claim 1 or 2, characterized bythat an RF laser is arranged in front of the input (I2) for the input signal to be digitized, which is controlled by means of the input signal to be digitized, wherein the input signal to be digitized is an electrical signal. [6] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that the optical reference signal is provided by a second CW laser (CW2). [7] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that a pulse shaper (PS) is arranged in front of the input (I3) for the pulsed laser signal. [8] Optically based analog-to-digital converter (1) according to claim 7, characterized by that the input signal for the pulse shaper (PS) is provided by a pulsed laser (PL) or by a first CW laser (CW1) with subsequent pulse shaper (PF). [9] Optically based analog-to-digital converter (1) according to one of the preceding claims 7 or 8, characterized by that a second splitter (SP2) is arranged immediately before the pulse shaper (PS), wherein a first part of the optical input signal to the second splitter (SP2) is made available to the pulse shaper (PS) during operation and a second part of the optical input signal is fed to the first input (I1) of the first combiner (C1) as a reference signal via an optical parametric oscillator (OPO). [10] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that the quantum pulse gate (QPG) is a multi-output quantum pulse gate. [11] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that the quantum pulse gate (QPG) has a poled nonlinear waveguide. [12] Optically based analog-to-digital converter (1) according to one of the preceding claims characterized by that the quantum pulse gate (QPG) comprises a poled lithium niobate waveguide and / or a poled potassium titanyl phosphate waveguide. [13] Optically based analog-to-digital converter (1) according to claim 11, characterized by that the nonlinear waveguide is periodically poled. [14] Optically based analog-to-digital converter (1) according to claim 11, characterized by that the nonlinear waveguide is aperiodically poled. [15] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that the evaluation unit (AE) has at least one optoelectronic conversion unit (OE). [16] Optically based analog-to-digital converter (1) according to one of the preceding claims, characterized by that the evaluation unit (AE) has a first optical bandpass filter (BP1). [17] Optically based analog-digital converter (1) according to one of the preceding claims, characterized by that the optical-based analog-to-digital converter is fully integrated. [18] Optically based analog-digital converter (1) according to one of the preceding claims 1 to 16, characterized by that the optical-based analog-to-digital converter is at least partially integrated. [19] Optically based analog-digital converter (1) according to one of the preceding claims 1 to 16, characterized by that the optical-based analog-to-digital converter is implemented with discrete components.

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